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Sourcecode: postgresql-8.4 version File versions

guc.c

/*--------------------------------------------------------------------
 * guc.c
 *
 * Support for grand unified configuration scheme, including SET
 * command, configuration file, and command line options.
 * See src/backend/utils/misc/README for more information.
 *
 *
 * Copyright (c) 2000-2009, PostgreSQL Global Development Group
 * Written by Peter Eisentraut <peter_e@gmx.net>.
 *
 * IDENTIFICATION
 *      $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.505 2009/06/11 14:49:06 momjian Exp $
 *
 *--------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include <float.h>
#include <math.h>
#include <limits.h>
#include <unistd.h>
#include <sys/stat.h>
#ifdef HAVE_SYSLOG
#include <syslog.h>
#endif

#include "access/gin.h"
#include "access/transam.h"
#include "access/twophase.h"
#include "access/xact.h"
#include "catalog/namespace.h"
#include "commands/async.h"
#include "commands/prepare.h"
#include "commands/vacuum.h"
#include "commands/variable.h"
#include "commands/trigger.h"
#include "funcapi.h"
#include "libpq/auth.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "parser/gramparse.h"
#include "parser/parse_expr.h"
#include "parser/parse_relation.h"
#include "parser/parse_type.h"
#include "parser/scansup.h"
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "postmaster/bgwriter.h"
#include "postmaster/postmaster.h"
#include "postmaster/syslogger.h"
#include "postmaster/walwriter.h"
#include "regex/regex.h"
#include "storage/bufmgr.h"
#include "storage/fd.h"
#include "tcop/tcopprot.h"
#include "tsearch/ts_cache.h"
#include "utils/builtins.h"
#include "utils/guc_tables.h"
#include "utils/memutils.h"
#include "utils/pg_locale.h"
#include "utils/plancache.h"
#include "utils/portal.h"
#include "utils/ps_status.h"
#include "utils/tzparser.h"
#include "utils/xml.h"

#ifndef PG_KRB_SRVTAB
#define PG_KRB_SRVTAB ""
#endif
#ifndef PG_KRB_SRVNAM
#define PG_KRB_SRVNAM ""
#endif

#define CONFIG_FILENAME "postgresql.conf"
#define HBA_FILENAME    "pg_hba.conf"
#define IDENT_FILENAME  "pg_ident.conf"

#ifdef EXEC_BACKEND
#define CONFIG_EXEC_PARAMS "global/config_exec_params"
#define CONFIG_EXEC_PARAMS_NEW "global/config_exec_params.new"
#endif

/* upper limit for GUC variables measured in kilobytes of memory */
#if SIZEOF_SIZE_T > 4
#define MAX_KILOBYTES   INT_MAX
#else
#define MAX_KILOBYTES   (INT_MAX / 1024)
#endif

#define KB_PER_MB (1024)
#define KB_PER_GB (1024*1024)

#define MS_PER_S 1000
#define S_PER_MIN 60
#define MS_PER_MIN (1000 * 60)
#define MIN_PER_H 60
#define S_PER_H (60 * 60)
#define MS_PER_H (1000 * 60 * 60)
#define MIN_PER_D (60 * 24)
#define S_PER_D (60 * 60 * 24)
#define MS_PER_D (1000 * 60 * 60 * 24)

/* XXX these should appear in other modules' header files */
extern bool Log_disconnections;
extern int  CommitDelay;
extern int  CommitSiblings;
extern char *default_tablespace;
extern char *temp_tablespaces;
extern bool synchronize_seqscans;
extern bool fullPageWrites;

#ifdef TRACE_SORT
extern bool trace_sort;
#endif
#ifdef TRACE_SYNCSCAN
extern bool trace_syncscan;
#endif
#ifdef DEBUG_BOUNDED_SORT
extern bool optimize_bounded_sort;
#endif

#ifdef USE_SSL
extern char *SSLCipherSuites;
#endif

static void set_config_sourcefile(const char *name, char *sourcefile,
                                int sourceline);

static const char *assign_log_destination(const char *value,
                                 bool doit, GucSource source);

#ifdef HAVE_SYSLOG
static int  syslog_facility = LOG_LOCAL0;

static bool assign_syslog_facility(int newval,
                                 bool doit, GucSource source);
static const char *assign_syslog_ident(const char *ident,
                              bool doit, GucSource source);
#endif

static bool assign_session_replication_role(int newval, bool doit,
                                                GucSource source);
static const char *show_num_temp_buffers(void);
static bool assign_phony_autocommit(bool newval, bool doit, GucSource source);
static const char *assign_custom_variable_classes(const char *newval, bool doit,
                                             GucSource source);
static bool assign_debug_assertions(bool newval, bool doit, GucSource source);
static bool assign_ssl(bool newval, bool doit, GucSource source);
static bool assign_stage_log_stats(bool newval, bool doit, GucSource source);
static bool assign_log_stats(bool newval, bool doit, GucSource source);
static bool assign_transaction_read_only(bool newval, bool doit, GucSource source);
static const char *assign_canonical_path(const char *newval, bool doit, GucSource source);
static const char *assign_timezone_abbreviations(const char *newval, bool doit, GucSource source);
static const char *show_archive_command(void);
static bool assign_tcp_keepalives_idle(int newval, bool doit, GucSource source);
static bool assign_tcp_keepalives_interval(int newval, bool doit, GucSource source);
static bool assign_tcp_keepalives_count(int newval, bool doit, GucSource source);
static const char *show_tcp_keepalives_idle(void);
static const char *show_tcp_keepalives_interval(void);
static const char *show_tcp_keepalives_count(void);
static bool assign_maxconnections(int newval, bool doit, GucSource source);
static bool assign_autovacuum_max_workers(int newval, bool doit, GucSource source);
static bool assign_effective_io_concurrency(int newval, bool doit, GucSource source);
static const char *assign_pgstat_temp_directory(const char *newval, bool doit, GucSource source);

static char *config_enum_get_options(struct config_enum * record,
                                    const char *prefix, const char *suffix,
                                    const char *separator);


/*
 * Options for enum values defined in this module.
 *
 * NOTE! Option values may not contain double quotes!
 */

/*
 * We have different sets for client and server message level options because
 * they sort slightly different (see "log" level)
 */
static const struct config_enum_entry client_message_level_options[] = {
      {"debug", DEBUG2, true},
      {"debug5", DEBUG5, false},
      {"debug4", DEBUG4, false},
      {"debug3", DEBUG3, false},
      {"debug2", DEBUG2, false},
      {"debug1", DEBUG1, false},
      {"log", LOG, false},
      {"info", INFO, true},
      {"notice", NOTICE, false},
      {"warning", WARNING, false},
      {"error", ERROR, false},
      {"fatal", FATAL, true},
      {"panic", PANIC, true},
      {NULL, 0, false}
};

static const struct config_enum_entry server_message_level_options[] = {
      {"debug", DEBUG2, true},
      {"debug5", DEBUG5, false},
      {"debug4", DEBUG4, false},
      {"debug3", DEBUG3, false},
      {"debug2", DEBUG2, false},
      {"debug1", DEBUG1, false},
      {"info", INFO, false},
      {"notice", NOTICE, false},
      {"warning", WARNING, false},
      {"error", ERROR, false},
      {"log", LOG, false},
      {"fatal", FATAL, false},
      {"panic", PANIC, false},
      {NULL, 0, false}
};

static const struct config_enum_entry intervalstyle_options[] = {
      {"postgres", INTSTYLE_POSTGRES, false},
      {"postgres_verbose", INTSTYLE_POSTGRES_VERBOSE, false},
      {"sql_standard", INTSTYLE_SQL_STANDARD, false},
      {"iso_8601", INTSTYLE_ISO_8601, false},
      {NULL, 0, false}
};

static const struct config_enum_entry log_error_verbosity_options[] = {
      {"terse", PGERROR_TERSE, false},
      {"default", PGERROR_DEFAULT, false},
      {"verbose", PGERROR_VERBOSE, false},
      {NULL, 0, false}
};

static const struct config_enum_entry log_statement_options[] = {
      {"none", LOGSTMT_NONE, false},
      {"ddl", LOGSTMT_DDL, false},
      {"mod", LOGSTMT_MOD, false},
      {"all", LOGSTMT_ALL, false},
      {NULL, 0, false}
};

static const struct config_enum_entry regex_flavor_options[] = {
      {"advanced", REG_ADVANCED, false},
      {"extended", REG_EXTENDED, false},
      {"basic", REG_BASIC, false},
      {NULL, 0, false}
};

static const struct config_enum_entry isolation_level_options[] = {
      {"serializable", XACT_SERIALIZABLE, false},
      {"repeatable read", XACT_REPEATABLE_READ, false},
      {"read committed", XACT_READ_COMMITTED, false},
      {"read uncommitted", XACT_READ_UNCOMMITTED, false},
      {NULL, 0}
};

static const struct config_enum_entry session_replication_role_options[] = {
      {"origin", SESSION_REPLICATION_ROLE_ORIGIN, false},
      {"replica", SESSION_REPLICATION_ROLE_REPLICA, false},
      {"local", SESSION_REPLICATION_ROLE_LOCAL, false},
      {NULL, 0, false}
};

#ifdef HAVE_SYSLOG
static const struct config_enum_entry syslog_facility_options[] = {
      {"local0", LOG_LOCAL0, false},
      {"local1", LOG_LOCAL1, false},
      {"local2", LOG_LOCAL2, false},
      {"local3", LOG_LOCAL3, false},
      {"local4", LOG_LOCAL4, false},
      {"local5", LOG_LOCAL5, false},
      {"local6", LOG_LOCAL6, false},
      {"local7", LOG_LOCAL7, false},
      {NULL, 0}
};
#endif

static const struct config_enum_entry track_function_options[] = {
      {"none", TRACK_FUNC_OFF, false},
      {"pl", TRACK_FUNC_PL, false},
      {"all", TRACK_FUNC_ALL, false},
      {NULL, 0, false}
};

static const struct config_enum_entry xmlbinary_options[] = {
      {"base64", XMLBINARY_BASE64, false},
      {"hex", XMLBINARY_HEX, false},
      {NULL, 0, false}
};

static const struct config_enum_entry xmloption_options[] = {
      {"content", XMLOPTION_CONTENT, false},
      {"document", XMLOPTION_DOCUMENT, false},
      {NULL, 0, false}
};

/*
 * Although only "on", "off", and "safe_encoding" are documented, we
 * accept all the likely variants of "on" and "off".
 */
static const struct config_enum_entry backslash_quote_options[] = {
      {"safe_encoding", BACKSLASH_QUOTE_SAFE_ENCODING, false},
      {"on", BACKSLASH_QUOTE_ON, false},
      {"off", BACKSLASH_QUOTE_OFF, false},
      {"true", BACKSLASH_QUOTE_ON, true},
      {"false", BACKSLASH_QUOTE_OFF, true},
      {"yes", BACKSLASH_QUOTE_ON, true},
      {"no", BACKSLASH_QUOTE_OFF, true},
      {"1", BACKSLASH_QUOTE_ON, true},
      {"0", BACKSLASH_QUOTE_OFF, true},
      {NULL, 0, false}
};

/*
 * Although only "on", "off", and "partition" are documented, we
 * accept all the likely variants of "on" and "off".
 */
static const struct config_enum_entry constraint_exclusion_options[] = {
      {"partition", CONSTRAINT_EXCLUSION_PARTITION, false},
      {"on", CONSTRAINT_EXCLUSION_ON, false},
      {"off", CONSTRAINT_EXCLUSION_OFF, false},
      {"true", CONSTRAINT_EXCLUSION_ON, true},
      {"false", CONSTRAINT_EXCLUSION_OFF, true},
      {"yes", CONSTRAINT_EXCLUSION_ON, true},
      {"no", CONSTRAINT_EXCLUSION_OFF, true},
      {"1", CONSTRAINT_EXCLUSION_ON, true},
      {"0", CONSTRAINT_EXCLUSION_OFF, true},
      {NULL, 0, false}
};

/*
 * Options for enum values stored in other modules
 */
extern const struct config_enum_entry sync_method_options[];

/*
 * GUC option variables that are exported from this module
 */
#ifdef USE_ASSERT_CHECKING
bool        assert_enabled = true;
#else
bool        assert_enabled = false;
#endif
bool        log_duration = false;
bool        Debug_print_plan = false;
bool        Debug_print_parse = false;
bool        Debug_print_rewritten = false;
bool        Debug_pretty_print = true;

bool        log_parser_stats = false;
bool        log_planner_stats = false;
bool        log_executor_stats = false;
bool        log_statement_stats = false;        /* this is sort of all three
                                                                         * above together */
bool        log_btree_build_stats = false;

bool        check_function_bodies = true;
bool        default_with_oids = false;
bool        SQL_inheritance = true;

bool        Password_encryption = true;

int               log_min_error_statement = ERROR;
int               log_min_messages = WARNING;
int               client_min_messages = NOTICE;
int               log_min_duration_statement = -1;
int               log_temp_files = -1;

int               num_temp_buffers = 1000;

char     *ConfigFileName;
char     *HbaFileName;
char     *IdentFileName;
char     *external_pid_file;

char     *pgstat_temp_directory;

int               tcp_keepalives_idle;
int               tcp_keepalives_interval;
int               tcp_keepalives_count;

/*
 * These variables are all dummies that don't do anything, except in some
 * cases provide the value for SHOW to display.  The real state is elsewhere
 * and is kept in sync by assign_hooks.
 */
static char *log_destination_string;

#ifdef HAVE_SYSLOG
static char *syslog_ident_str;
#endif
static bool phony_autocommit;
static bool session_auth_is_superuser;
static double phony_random_seed;
static char *client_encoding_string;
static char *datestyle_string;
static char *locale_collate;
static char *locale_ctype;
static char *server_encoding_string;
static char *server_version_string;
static int  server_version_num;
static char *timezone_string;
static char *log_timezone_string;
static char *timezone_abbreviations_string;
static char *XactIsoLevel_string;
static char *data_directory;
static char *custom_variable_classes;
static int  max_function_args;
static int  max_index_keys;
static int  max_identifier_length;
static int  block_size;
static int  segment_size;
static int  wal_block_size;
static int  wal_segment_size;
static bool integer_datetimes;
static int  effective_io_concurrency;

/* should be static, but commands/variable.c needs to get at these */
char     *role_string;
char     *session_authorization_string;


/*
 * Displayable names for context types (enum GucContext)
 *
 * Note: these strings are deliberately not localized.
 */
const char *const GucContext_Names[] =
{
       /* PGC_INTERNAL */ "internal",
       /* PGC_POSTMASTER */ "postmaster",
       /* PGC_SIGHUP */ "sighup",
       /* PGC_BACKEND */ "backend",
       /* PGC_SUSET */ "superuser",
       /* PGC_USERSET */ "user"
};

/*
 * Displayable names for source types (enum GucSource)
 *
 * Note: these strings are deliberately not localized.
 */
const char *const GucSource_Names[] =
{
       /* PGC_S_DEFAULT */ "default",
       /* PGC_S_ENV_VAR */ "environment variable",
       /* PGC_S_FILE */ "configuration file",
       /* PGC_S_ARGV */ "command line",
       /* PGC_S_DATABASE */ "database",
       /* PGC_S_USER */ "user",
       /* PGC_S_CLIENT */ "client",
       /* PGC_S_OVERRIDE */ "override",
       /* PGC_S_INTERACTIVE */ "interactive",
       /* PGC_S_TEST */ "test",
       /* PGC_S_SESSION */ "session"
};

/*
 * Displayable names for the groupings defined in enum config_group
 */
const char *const config_group_names[] =
{
      /* UNGROUPED */
      gettext_noop("Ungrouped"),
      /* FILE_LOCATIONS */
      gettext_noop("File Locations"),
      /* CONN_AUTH */
      gettext_noop("Connections and Authentication"),
      /* CONN_AUTH_SETTINGS */
      gettext_noop("Connections and Authentication / Connection Settings"),
      /* CONN_AUTH_SECURITY */
      gettext_noop("Connections and Authentication / Security and Authentication"),
      /* RESOURCES */
      gettext_noop("Resource Usage"),
      /* RESOURCES_MEM */
      gettext_noop("Resource Usage / Memory"),
      /* RESOURCES_KERNEL */
      gettext_noop("Resource Usage / Kernel Resources"),
      /* WAL */
      gettext_noop("Write-Ahead Log"),
      /* WAL_SETTINGS */
      gettext_noop("Write-Ahead Log / Settings"),
      /* WAL_CHECKPOINTS */
      gettext_noop("Write-Ahead Log / Checkpoints"),
      /* QUERY_TUNING */
      gettext_noop("Query Tuning"),
      /* QUERY_TUNING_METHOD */
      gettext_noop("Query Tuning / Planner Method Configuration"),
      /* QUERY_TUNING_COST */
      gettext_noop("Query Tuning / Planner Cost Constants"),
      /* QUERY_TUNING_GEQO */
      gettext_noop("Query Tuning / Genetic Query Optimizer"),
      /* QUERY_TUNING_OTHER */
      gettext_noop("Query Tuning / Other Planner Options"),
      /* LOGGING */
      gettext_noop("Reporting and Logging"),
      /* LOGGING_WHERE */
      gettext_noop("Reporting and Logging / Where to Log"),
      /* LOGGING_WHEN */
      gettext_noop("Reporting and Logging / When to Log"),
      /* LOGGING_WHAT */
      gettext_noop("Reporting and Logging / What to Log"),
      /* STATS */
      gettext_noop("Statistics"),
      /* STATS_MONITORING */
      gettext_noop("Statistics / Monitoring"),
      /* STATS_COLLECTOR */
      gettext_noop("Statistics / Query and Index Statistics Collector"),
      /* AUTOVACUUM */
      gettext_noop("Autovacuum"),
      /* CLIENT_CONN */
      gettext_noop("Client Connection Defaults"),
      /* CLIENT_CONN_STATEMENT */
      gettext_noop("Client Connection Defaults / Statement Behavior"),
      /* CLIENT_CONN_LOCALE */
      gettext_noop("Client Connection Defaults / Locale and Formatting"),
      /* CLIENT_CONN_OTHER */
      gettext_noop("Client Connection Defaults / Other Defaults"),
      /* LOCK_MANAGEMENT */
      gettext_noop("Lock Management"),
      /* COMPAT_OPTIONS */
      gettext_noop("Version and Platform Compatibility"),
      /* COMPAT_OPTIONS_PREVIOUS */
      gettext_noop("Version and Platform Compatibility / Previous PostgreSQL Versions"),
      /* COMPAT_OPTIONS_CLIENT */
      gettext_noop("Version and Platform Compatibility / Other Platforms and Clients"),
      /* PRESET_OPTIONS */
      gettext_noop("Preset Options"),
      /* CUSTOM_OPTIONS */
      gettext_noop("Customized Options"),
      /* DEVELOPER_OPTIONS */
      gettext_noop("Developer Options"),
      /* help_config wants this array to be null-terminated */
      NULL
};

/*
 * Displayable names for GUC variable types (enum config_type)
 *
 * Note: these strings are deliberately not localized.
 */
const char *const config_type_names[] =
{
       /* PGC_BOOL */ "bool",
       /* PGC_INT */ "integer",
       /* PGC_REAL */ "real",
       /* PGC_STRING */ "string",
       /* PGC_ENUM */ "enum"
};


/*
 * Contents of GUC tables
 *
 * See src/backend/utils/misc/README for design notes.
 *
 * TO ADD AN OPTION:
 *
 * 1. Declare a global variable of type bool, int, double, or char*
 *      and make use of it.
 *
 * 2. Decide at what times it's safe to set the option. See guc.h for
 *      details.
 *
 * 3. Decide on a name, a default value, upper and lower bounds (if
 *      applicable), etc.
 *
 * 4. Add a record below.
 *
 * 5. Add it to src/backend/utils/misc/postgresql.conf.sample, if
 *      appropriate.
 *
 * 6. Don't forget to document the option (at least in config.sgml).
 *
 * 7. If it's a new GUC_LIST option you must edit pg_dumpall.c to ensure
 *      it is not single quoted at dump time.
 */


/******** option records follow ********/

static struct config_bool ConfigureNamesBool[] =
{
      {
            {"enable_seqscan", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enables the planner's use of sequential-scan plans."),
                  NULL
            },
            &enable_seqscan,
            true, NULL, NULL
      },
      {
            {"enable_indexscan", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enables the planner's use of index-scan plans."),
                  NULL
            },
            &enable_indexscan,
            true, NULL, NULL
      },
      {
            {"enable_bitmapscan", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enables the planner's use of bitmap-scan plans."),
                  NULL
            },
            &enable_bitmapscan,
            true, NULL, NULL
      },
      {
            {"enable_tidscan", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enables the planner's use of TID scan plans."),
                  NULL
            },
            &enable_tidscan,
            true, NULL, NULL
      },
      {
            {"enable_sort", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enables the planner's use of explicit sort steps."),
                  NULL
            },
            &enable_sort,
            true, NULL, NULL
      },
      {
            {"enable_hashagg", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enables the planner's use of hashed aggregation plans."),
                  NULL
            },
            &enable_hashagg,
            true, NULL, NULL
      },
      {
            {"enable_nestloop", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enables the planner's use of nested-loop join plans."),
                  NULL
            },
            &enable_nestloop,
            true, NULL, NULL
      },
      {
            {"enable_mergejoin", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enables the planner's use of merge join plans."),
                  NULL
            },
            &enable_mergejoin,
            true, NULL, NULL
      },
      {
            {"enable_hashjoin", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enables the planner's use of hash join plans."),
                  NULL
            },
            &enable_hashjoin,
            true, NULL, NULL
      },
      {
            {"geqo", PGC_USERSET, QUERY_TUNING_GEQO,
                  gettext_noop("Enables genetic query optimization."),
                  gettext_noop("This algorithm attempts to do planning without "
                                     "exhaustive searching.")
            },
            &enable_geqo,
            true, NULL, NULL
      },
      {
            /* Not for general use --- used by SET SESSION AUTHORIZATION */
            {"is_superuser", PGC_INTERNAL, UNGROUPED,
                  gettext_noop("Shows whether the current user is a superuser."),
                  NULL,
                  GUC_REPORT | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &session_auth_is_superuser,
            false, NULL, NULL
      },
      {
            {"ssl", PGC_POSTMASTER, CONN_AUTH_SECURITY,
                  gettext_noop("Enables SSL connections."),
                  NULL
            },
            &EnableSSL,
            false, assign_ssl, NULL
      },
      {
            {"fsync", PGC_SIGHUP, WAL_SETTINGS,
                  gettext_noop("Forces synchronization of updates to disk."),
                  gettext_noop("The server will use the fsync() system call in several places to make "
                  "sure that updates are physically written to disk. This insures "
                                     "that a database cluster will recover to a consistent state after "
                                     "an operating system or hardware crash.")
            },
            &enableFsync,
            true, NULL, NULL
      },
      {
            {"synchronous_commit", PGC_USERSET, WAL_SETTINGS,
                  gettext_noop("Sets immediate fsync at commit."),
                  NULL
            },
            &XactSyncCommit,
            true, NULL, NULL
      },
      {
            {"zero_damaged_pages", PGC_SUSET, DEVELOPER_OPTIONS,
                  gettext_noop("Continues processing past damaged page headers."),
                  gettext_noop("Detection of a damaged page header normally causes PostgreSQL to "
                        "report an error, aborting the current transaction. Setting "
                                     "zero_damaged_pages to true causes the system to instead report a "
                                     "warning, zero out the damaged page, and continue processing. This "
                                     "behavior will destroy data, namely all the rows on the damaged page."),
                  GUC_NOT_IN_SAMPLE
            },
            &zero_damaged_pages,
            false, NULL, NULL
      },
      {
            {"full_page_writes", PGC_SIGHUP, WAL_SETTINGS,
                  gettext_noop("Writes full pages to WAL when first modified after a checkpoint."),
                  gettext_noop("A page write in process during an operating system crash might be "
                                     "only partially written to disk.  During recovery, the row changes "
                    "stored in WAL are not enough to recover.  This option writes "
                                     "pages when first modified after a checkpoint to WAL so full recovery "
                                     "is possible.")
            },
            &fullPageWrites,
            true, NULL, NULL
      },
      {
            {"silent_mode", PGC_POSTMASTER, LOGGING_WHEN,
                  gettext_noop("Runs the server silently."),
                  gettext_noop("If this parameter is set, the server will automatically run in the "
                         "background and any controlling terminals are dissociated.")
            },
            &SilentMode,
            false, NULL, NULL
      },
      {
            {"log_checkpoints", PGC_SIGHUP, LOGGING_WHAT,
                  gettext_noop("Logs each checkpoint."),
                  NULL
            },
            &log_checkpoints,
            false, NULL, NULL
      },
      {
            {"log_connections", PGC_BACKEND, LOGGING_WHAT,
                  gettext_noop("Logs each successful connection."),
                  NULL
            },
            &Log_connections,
            false, NULL, NULL
      },
      {
            {"log_disconnections", PGC_BACKEND, LOGGING_WHAT,
                  gettext_noop("Logs end of a session, including duration."),
                  NULL
            },
            &Log_disconnections,
            false, NULL, NULL
      },
      {
            {"debug_assertions", PGC_USERSET, DEVELOPER_OPTIONS,
                  gettext_noop("Turns on various assertion checks."),
                  gettext_noop("This is a debugging aid."),
                  GUC_NOT_IN_SAMPLE
            },
            &assert_enabled,
#ifdef USE_ASSERT_CHECKING
            true,
#else
            false,
#endif
            assign_debug_assertions, NULL
      },
      {
            /* currently undocumented, so don't show in SHOW ALL */
            {"exit_on_error", PGC_USERSET, UNGROUPED,
                  gettext_noop("No description available."),
                  NULL,
                  GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE
            },
            &ExitOnAnyError,
            false, NULL, NULL
      },
      {
            {"log_duration", PGC_SUSET, LOGGING_WHAT,
                  gettext_noop("Logs the duration of each completed SQL statement."),
                  NULL
            },
            &log_duration,
            false, NULL, NULL
      },
      {
            {"debug_print_parse", PGC_USERSET, LOGGING_WHAT,
                  gettext_noop("Logs each query's parse tree."),
                  NULL
            },
            &Debug_print_parse,
            false, NULL, NULL
      },
      {
            {"debug_print_rewritten", PGC_USERSET, LOGGING_WHAT,
                  gettext_noop("Logs each query's rewritten parse tree."),
                  NULL
            },
            &Debug_print_rewritten,
            false, NULL, NULL
      },
      {
            {"debug_print_plan", PGC_USERSET, LOGGING_WHAT,
                  gettext_noop("Logs each query's execution plan."),
                  NULL
            },
            &Debug_print_plan,
            false, NULL, NULL
      },
      {
            {"debug_pretty_print", PGC_USERSET, LOGGING_WHAT,
                  gettext_noop("Indents parse and plan tree displays."),
                  NULL
            },
            &Debug_pretty_print,
            true, NULL, NULL
      },
      {
            {"log_parser_stats", PGC_SUSET, STATS_MONITORING,
                  gettext_noop("Writes parser performance statistics to the server log."),
                  NULL
            },
            &log_parser_stats,
            false, assign_stage_log_stats, NULL
      },
      {
            {"log_planner_stats", PGC_SUSET, STATS_MONITORING,
                  gettext_noop("Writes planner performance statistics to the server log."),
                  NULL
            },
            &log_planner_stats,
            false, assign_stage_log_stats, NULL
      },
      {
            {"log_executor_stats", PGC_SUSET, STATS_MONITORING,
                  gettext_noop("Writes executor performance statistics to the server log."),
                  NULL
            },
            &log_executor_stats,
            false, assign_stage_log_stats, NULL
      },
      {
            {"log_statement_stats", PGC_SUSET, STATS_MONITORING,
                  gettext_noop("Writes cumulative performance statistics to the server log."),
                  NULL
            },
            &log_statement_stats,
            false, assign_log_stats, NULL
      },
#ifdef BTREE_BUILD_STATS
      {
            {"log_btree_build_stats", PGC_SUSET, DEVELOPER_OPTIONS,
                  gettext_noop("No description available."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &log_btree_build_stats,
            false, NULL, NULL
      },
#endif

      {
            {"track_activities", PGC_SUSET, STATS_COLLECTOR,
                  gettext_noop("Collects information about executing commands."),
                  gettext_noop("Enables the collection of information on the currently "
                                     "executing command of each session, along with "
                                     "the time at which that command began execution.")
            },
            &pgstat_track_activities,
            true, NULL, NULL
      },
      {
            {"track_counts", PGC_SUSET, STATS_COLLECTOR,
                  gettext_noop("Collects statistics on database activity."),
                  NULL
            },
            &pgstat_track_counts,
            true, NULL, NULL
      },

      {
            {"update_process_title", PGC_SUSET, STATS_COLLECTOR,
                  gettext_noop("Updates the process title to show the active SQL command."),
                  gettext_noop("Enables updating of the process title every time a new SQL command is received by the server.")
            },
            &update_process_title,
            true, NULL, NULL
      },

      {
            {"autovacuum", PGC_SIGHUP, AUTOVACUUM,
                  gettext_noop("Starts the autovacuum subprocess."),
                  NULL
            },
            &autovacuum_start_daemon,
            true, NULL, NULL
      },

      {
            {"trace_notify", PGC_USERSET, DEVELOPER_OPTIONS,
                  gettext_noop("Generates debugging output for LISTEN and NOTIFY."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &Trace_notify,
            false, NULL, NULL
      },

#ifdef LOCK_DEBUG
      {
            {"trace_locks", PGC_SUSET, DEVELOPER_OPTIONS,
                  gettext_noop("No description available."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &Trace_locks,
            false, NULL, NULL
      },
      {
            {"trace_userlocks", PGC_SUSET, DEVELOPER_OPTIONS,
                  gettext_noop("No description available."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &Trace_userlocks,
            false, NULL, NULL
      },
      {
            {"trace_lwlocks", PGC_SUSET, DEVELOPER_OPTIONS,
                  gettext_noop("No description available."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &Trace_lwlocks,
            false, NULL, NULL
      },
      {
            {"debug_deadlocks", PGC_SUSET, DEVELOPER_OPTIONS,
                  gettext_noop("No description available."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &Debug_deadlocks,
            false, NULL, NULL
      },
#endif

      {
            {"log_lock_waits", PGC_SUSET, LOGGING_WHAT,
                  gettext_noop("Logs long lock waits."),
                  NULL
            },
            &log_lock_waits,
            false, NULL, NULL
      },

      {
            {"log_hostname", PGC_SIGHUP, LOGGING_WHAT,
                  gettext_noop("Logs the host name in the connection logs."),
                  gettext_noop("By default, connection logs only show the IP address "
                                     "of the connecting host. If you want them to show the host name you "
                    "can turn this on, but depending on your host name resolution "
                     "setup it might impose a non-negligible performance penalty.")
            },
            &log_hostname,
            false, NULL, NULL
      },
      {
            {"sql_inheritance", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                  gettext_noop("Causes subtables to be included by default in various commands."),
                  NULL
            },
            &SQL_inheritance,
            true, NULL, NULL
      },
      {
            {"password_encryption", PGC_USERSET, CONN_AUTH_SECURITY,
                  gettext_noop("Encrypt passwords."),
                  gettext_noop("When a password is specified in CREATE USER or "
                     "ALTER USER without writing either ENCRYPTED or UNENCRYPTED, "
                                     "this parameter determines whether the password is to be encrypted.")
            },
            &Password_encryption,
            true, NULL, NULL
      },
      {
            {"transform_null_equals", PGC_USERSET, COMPAT_OPTIONS_CLIENT,
                  gettext_noop("Treats \"expr=NULL\" as \"expr IS NULL\"."),
                  gettext_noop("When turned on, expressions of the form expr = NULL "
                     "(or NULL = expr) are treated as expr IS NULL, that is, they "
                        "return true if expr evaluates to the null value, and false "
                     "otherwise. The correct behavior of expr = NULL is to always "
                                     "return null (unknown).")
            },
            &Transform_null_equals,
            false, NULL, NULL
      },
      {
            {"db_user_namespace", PGC_SIGHUP, CONN_AUTH_SECURITY,
                  gettext_noop("Enables per-database user names."),
                  NULL
            },
            &Db_user_namespace,
            false, NULL, NULL
      },
      {
            /* only here for backwards compatibility */
            {"autocommit", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("This parameter doesn't do anything."),
                  gettext_noop("It's just here so that we won't choke on SET AUTOCOMMIT TO ON from 7.3-vintage clients."),
                  GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE
            },
            &phony_autocommit,
            true, assign_phony_autocommit, NULL
      },
      {
            {"default_transaction_read_only", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets the default read-only status of new transactions."),
                  NULL
            },
            &DefaultXactReadOnly,
            false, NULL, NULL
      },
      {
            {"transaction_read_only", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets the current transaction's read-only status."),
                  NULL,
                  GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &XactReadOnly,
            false, assign_transaction_read_only, NULL
      },
      {
            {"add_missing_from", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                  gettext_noop("Automatically adds missing table references to FROM clauses."),
                  NULL
            },
            &add_missing_from,
            false, NULL, NULL
      },
      {
            {"check_function_bodies", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Check function bodies during CREATE FUNCTION."),
                  NULL
            },
            &check_function_bodies,
            true, NULL, NULL
      },
      {
            {"array_nulls", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                  gettext_noop("Enable input of NULL elements in arrays."),
                  gettext_noop("When turned on, unquoted NULL in an array input "
                                     "value means a null value; "
                                     "otherwise it is taken literally.")
            },
            &Array_nulls,
            true, NULL, NULL
      },
      {
            {"default_with_oids", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                  gettext_noop("Create new tables with OIDs by default."),
                  NULL
            },
            &default_with_oids,
            false, NULL, NULL
      },
      {
            {"logging_collector", PGC_POSTMASTER, LOGGING_WHERE,
                  gettext_noop("Start a subprocess to capture stderr output and/or csvlogs into log files."),
                  NULL
            },
            &Logging_collector,
            false, NULL, NULL
      },
      {
            {"log_truncate_on_rotation", PGC_SIGHUP, LOGGING_WHERE,
                  gettext_noop("Truncate existing log files of same name during log rotation."),
                  NULL
            },
            &Log_truncate_on_rotation,
            false, NULL, NULL
      },

#ifdef TRACE_SORT
      {
            {"trace_sort", PGC_USERSET, DEVELOPER_OPTIONS,
                  gettext_noop("Emit information about resource usage in sorting."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &trace_sort,
            false, NULL, NULL
      },
#endif

#ifdef TRACE_SYNCSCAN
      /* this is undocumented because not exposed in a standard build */
      {
            {"trace_syncscan", PGC_USERSET, DEVELOPER_OPTIONS,
                  gettext_noop("Generate debugging output for synchronized scanning."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &trace_syncscan,
            false, NULL, NULL
      },
#endif

#ifdef DEBUG_BOUNDED_SORT
      /* this is undocumented because not exposed in a standard build */
      {
            {
                  "optimize_bounded_sort", PGC_USERSET, QUERY_TUNING_METHOD,
                  gettext_noop("Enable bounded sorting using heap sort."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &optimize_bounded_sort,
            true, NULL, NULL
      },
#endif

#ifdef WAL_DEBUG
      {
            {"wal_debug", PGC_SUSET, DEVELOPER_OPTIONS,
                  gettext_noop("Emit WAL-related debugging output."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &XLOG_DEBUG,
            false, NULL, NULL
      },
#endif

      {
            {"integer_datetimes", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Datetimes are integer based."),
                  NULL,
                  GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &integer_datetimes,
#ifdef HAVE_INT64_TIMESTAMP
            true, NULL, NULL
#else
            false, NULL, NULL
#endif
      },

      {
            {"krb_caseins_users", PGC_SIGHUP, CONN_AUTH_SECURITY,
                  gettext_noop("Sets whether Kerberos and GSSAPI user names should be treated as case-insensitive."),
                  NULL
            },
            &pg_krb_caseins_users,
            false, NULL, NULL
      },

      {
            {"escape_string_warning", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                  gettext_noop("Warn about backslash escapes in ordinary string literals."),
                  NULL
            },
            &escape_string_warning,
            true, NULL, NULL
      },

      {
            {"standard_conforming_strings", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                  gettext_noop("Causes '...' strings to treat backslashes literally."),
                  NULL,
                  GUC_REPORT
            },
            &standard_conforming_strings,
            false, NULL, NULL
      },

      {
            {"synchronize_seqscans", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                  gettext_noop("Enable synchronized sequential scans."),
                  NULL
            },
            &synchronize_seqscans,
            true, NULL, NULL
      },

      {
            {"archive_mode", PGC_POSTMASTER, WAL_SETTINGS,
                  gettext_noop("Allows archiving of WAL files using archive_command."),
                  NULL
            },
            &XLogArchiveMode,
            false, NULL, NULL
      },

      {
            {"allow_system_table_mods", PGC_POSTMASTER, DEVELOPER_OPTIONS,
                  gettext_noop("Allows modifications of the structure of system tables."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &allowSystemTableMods,
            false, NULL, NULL
      },

      {
            {"ignore_system_indexes", PGC_BACKEND, DEVELOPER_OPTIONS,
                  gettext_noop("Disables reading from system indexes."),
                  gettext_noop("It does not prevent updating the indexes, so it is safe "
                                     "to use.  The worst consequence is slowness."),
                  GUC_NOT_IN_SAMPLE
            },
            &IgnoreSystemIndexes,
            false, NULL, NULL
      },

      /* End-of-list marker */
      {
            {NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL
      }
};


static struct config_int ConfigureNamesInt[] =
{
      {
            {"archive_timeout", PGC_SIGHUP, WAL_SETTINGS,
                  gettext_noop("Forces a switch to the next xlog file if a "
                                     "new file has not been started within N seconds."),
                  NULL,
                  GUC_UNIT_S
            },
            &XLogArchiveTimeout,
            0, 0, INT_MAX, NULL, NULL
      },
      {
            {"post_auth_delay", PGC_BACKEND, DEVELOPER_OPTIONS,
                  gettext_noop("Waits N seconds on connection startup after authentication."),
                  gettext_noop("This allows attaching a debugger to the process."),
                  GUC_NOT_IN_SAMPLE | GUC_UNIT_S
            },
            &PostAuthDelay,
            0, 0, INT_MAX, NULL, NULL
      },
      {
            {"default_statistics_target", PGC_USERSET, QUERY_TUNING_OTHER,
                  gettext_noop("Sets the default statistics target."),
                  gettext_noop("This applies to table columns that have not had a "
                        "column-specific target set via ALTER TABLE SET STATISTICS.")
            },
            &default_statistics_target,
            100, 1, 10000, NULL, NULL
      },
      {
            {"from_collapse_limit", PGC_USERSET, QUERY_TUNING_OTHER,
                  gettext_noop("Sets the FROM-list size beyond which subqueries "
                                     "are not collapsed."),
                  gettext_noop("The planner will merge subqueries into upper "
                        "queries if the resulting FROM list would have no more than "
                                     "this many items.")
            },
            &from_collapse_limit,
            8, 1, INT_MAX, NULL, NULL
      },
      {
            {"join_collapse_limit", PGC_USERSET, QUERY_TUNING_OTHER,
                  gettext_noop("Sets the FROM-list size beyond which JOIN "
                                     "constructs are not flattened."),
                  gettext_noop("The planner will flatten explicit JOIN "
                                     "constructs into lists of FROM items whenever a "
                                     "list of no more than this many items would result.")
            },
            &join_collapse_limit,
            8, 1, INT_MAX, NULL, NULL
      },
      {
            {"geqo_threshold", PGC_USERSET, QUERY_TUNING_GEQO,
                  gettext_noop("Sets the threshold of FROM items beyond which GEQO is used."),
                  NULL
            },
            &geqo_threshold,
            12, 2, INT_MAX, NULL, NULL
      },
      {
            {"geqo_effort", PGC_USERSET, QUERY_TUNING_GEQO,
                  gettext_noop("GEQO: effort is used to set the default for other GEQO parameters."),
                  NULL
            },
            &Geqo_effort,
            DEFAULT_GEQO_EFFORT, MIN_GEQO_EFFORT, MAX_GEQO_EFFORT, NULL, NULL
      },
      {
            {"geqo_pool_size", PGC_USERSET, QUERY_TUNING_GEQO,
                  gettext_noop("GEQO: number of individuals in the population."),
                  gettext_noop("Zero selects a suitable default value.")
            },
            &Geqo_pool_size,
            0, 0, INT_MAX, NULL, NULL
      },
      {
            {"geqo_generations", PGC_USERSET, QUERY_TUNING_GEQO,
                  gettext_noop("GEQO: number of iterations of the algorithm."),
                  gettext_noop("Zero selects a suitable default value.")
            },
            &Geqo_generations,
            0, 0, INT_MAX, NULL, NULL
      },

      {
            /* This is PGC_SIGHUP so all backends have the same value. */
            {"deadlock_timeout", PGC_SIGHUP, LOCK_MANAGEMENT,
                  gettext_noop("Sets the time to wait on a lock before checking for deadlock."),
                  NULL,
                  GUC_UNIT_MS
            },
            &DeadlockTimeout,
            1000, 1, INT_MAX / 1000, NULL, NULL
      },

      /*
       * Note: MaxBackends is limited to INT_MAX/4 because some places compute
       * 4*MaxBackends without any overflow check.  This check is made in
       * assign_maxconnections, since MaxBackends is computed as MaxConnections
       * plus autovacuum_max_workers.
       *
       * Likewise we have to limit NBuffers to INT_MAX/2.
       */
      {
            {"max_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                  gettext_noop("Sets the maximum number of concurrent connections."),
                  NULL
            },
            &MaxConnections,
            100, 1, INT_MAX / 4, assign_maxconnections, NULL
      },

      {
            {"superuser_reserved_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                  gettext_noop("Sets the number of connection slots reserved for superusers."),
                  NULL
            },
            &ReservedBackends,
            3, 0, INT_MAX / 4, NULL, NULL
      },

      {
            {"shared_buffers", PGC_POSTMASTER, RESOURCES_MEM,
                  gettext_noop("Sets the number of shared memory buffers used by the server."),
                  NULL,
                  GUC_UNIT_BLOCKS
            },
            &NBuffers,
            1024, 16, INT_MAX / 2, NULL, NULL
      },

      {
            {"temp_buffers", PGC_USERSET, RESOURCES_MEM,
                  gettext_noop("Sets the maximum number of temporary buffers used by each session."),
                  NULL,
                  GUC_UNIT_BLOCKS
            },
            &num_temp_buffers,
            1024, 100, INT_MAX / 2, NULL, show_num_temp_buffers
      },

      {
            {"port", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                  gettext_noop("Sets the TCP port the server listens on."),
                  NULL
            },
            &PostPortNumber,
            DEF_PGPORT, 1, 65535, NULL, NULL
      },

      {
            {"unix_socket_permissions", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                  gettext_noop("Sets the access permissions of the Unix-domain socket."),
                  gettext_noop("Unix-domain sockets use the usual Unix file system "
                                     "permission set. The parameter value is expected to be a numeric mode "
                                     "specification in the form accepted by the chmod and umask system "
                                     "calls. (To use the customary octal format the number must start with "
                                     "a 0 (zero).)")
            },
            &Unix_socket_permissions,
            0777, 0000, 0777, NULL, NULL
      },

      {
            {"work_mem", PGC_USERSET, RESOURCES_MEM,
                  gettext_noop("Sets the maximum memory to be used for query workspaces."),
                  gettext_noop("This much memory can be used by each internal "
                                     "sort operation and hash table before switching to "
                                     "temporary disk files."),
                  GUC_UNIT_KB
            },
            &work_mem,
            1024, 64, MAX_KILOBYTES, NULL, NULL
      },

      {
            {"maintenance_work_mem", PGC_USERSET, RESOURCES_MEM,
                  gettext_noop("Sets the maximum memory to be used for maintenance operations."),
                  gettext_noop("This includes operations such as VACUUM and CREATE INDEX."),
                  GUC_UNIT_KB
            },
            &maintenance_work_mem,
            16384, 1024, MAX_KILOBYTES, NULL, NULL
      },

      {
            {"max_stack_depth", PGC_SUSET, RESOURCES_MEM,
                  gettext_noop("Sets the maximum stack depth, in kilobytes."),
                  NULL,
                  GUC_UNIT_KB
            },
            &max_stack_depth,
            100, 100, MAX_KILOBYTES, assign_max_stack_depth, NULL
      },

      {
            {"vacuum_cost_page_hit", PGC_USERSET, RESOURCES,
                  gettext_noop("Vacuum cost for a page found in the buffer cache."),
                  NULL
            },
            &VacuumCostPageHit,
            1, 0, 10000, NULL, NULL
      },

      {
            {"vacuum_cost_page_miss", PGC_USERSET, RESOURCES,
                  gettext_noop("Vacuum cost for a page not found in the buffer cache."),
                  NULL
            },
            &VacuumCostPageMiss,
            10, 0, 10000, NULL, NULL
      },

      {
            {"vacuum_cost_page_dirty", PGC_USERSET, RESOURCES,
                  gettext_noop("Vacuum cost for a page dirtied by vacuum."),
                  NULL
            },
            &VacuumCostPageDirty,
            20, 0, 10000, NULL, NULL
      },

      {
            {"vacuum_cost_limit", PGC_USERSET, RESOURCES,
                  gettext_noop("Vacuum cost amount available before napping."),
                  NULL
            },
            &VacuumCostLimit,
            200, 1, 10000, NULL, NULL
      },

      {
            {"vacuum_cost_delay", PGC_USERSET, RESOURCES,
                  gettext_noop("Vacuum cost delay in milliseconds."),
                  NULL,
                  GUC_UNIT_MS
            },
            &VacuumCostDelay,
            0, 0, 100, NULL, NULL
      },

      {
            {"autovacuum_vacuum_cost_delay", PGC_SIGHUP, AUTOVACUUM,
                  gettext_noop("Vacuum cost delay in milliseconds, for autovacuum."),
                  NULL,
                  GUC_UNIT_MS
            },
            &autovacuum_vac_cost_delay,
            20, -1, 100, NULL, NULL
      },

      {
            {"autovacuum_vacuum_cost_limit", PGC_SIGHUP, AUTOVACUUM,
                  gettext_noop("Vacuum cost amount available before napping, for autovacuum."),
                  NULL
            },
            &autovacuum_vac_cost_limit,
            -1, -1, 10000, NULL, NULL
      },

      {
            {"max_files_per_process", PGC_POSTMASTER, RESOURCES_KERNEL,
                  gettext_noop("Sets the maximum number of simultaneously open files for each server process."),
                  NULL
            },
            &max_files_per_process,
            1000, 25, INT_MAX, NULL, NULL
      },

      {
            {"max_prepared_transactions", PGC_POSTMASTER, RESOURCES,
                  gettext_noop("Sets the maximum number of simultaneously prepared transactions."),
                  NULL
            },
            &max_prepared_xacts,
            0, 0, INT_MAX / 4, NULL, NULL
      },

#ifdef LOCK_DEBUG
      {
            {"trace_lock_oidmin", PGC_SUSET, DEVELOPER_OPTIONS,
                  gettext_noop("No description available."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &Trace_lock_oidmin,
            FirstNormalObjectId, 0, INT_MAX, NULL, NULL
      },
      {
            {"trace_lock_table", PGC_SUSET, DEVELOPER_OPTIONS,
                  gettext_noop("No description available."),
                  NULL,
                  GUC_NOT_IN_SAMPLE
            },
            &Trace_lock_table,
            0, 0, INT_MAX, NULL, NULL
      },
#endif

      {
            {"statement_timeout", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets the maximum allowed duration of any statement."),
                  gettext_noop("A value of 0 turns off the timeout."),
                  GUC_UNIT_MS
            },
            &StatementTimeout,
            0, 0, INT_MAX, NULL, NULL
      },

      {
            {"vacuum_freeze_min_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Minimum age at which VACUUM should freeze a table row."),
                  NULL
            },
            &vacuum_freeze_min_age,
            50000000, 0, 1000000000, NULL, NULL
      },

      {
            {"vacuum_freeze_table_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Age at which VACUUM should scan whole table to freeze tuples."),
                  NULL
            },
            &vacuum_freeze_table_age,
            150000000, 0, 2000000000, NULL, NULL
      },

      {
            {"max_locks_per_transaction", PGC_POSTMASTER, LOCK_MANAGEMENT,
                  gettext_noop("Sets the maximum number of locks per transaction."),
                  gettext_noop("The shared lock table is sized on the assumption that "
                    "at most max_locks_per_transaction * max_connections distinct "
                                     "objects will need to be locked at any one time.")
            },
            &max_locks_per_xact,
            64, 10, INT_MAX, NULL, NULL
      },

      {
            {"authentication_timeout", PGC_SIGHUP, CONN_AUTH_SECURITY,
                  gettext_noop("Sets the maximum allowed time to complete client authentication."),
                  NULL,
                  GUC_UNIT_S
            },
            &AuthenticationTimeout,
            60, 1, 600, NULL, NULL
      },

      {
            /* Not for general use */
            {"pre_auth_delay", PGC_SIGHUP, DEVELOPER_OPTIONS,
                  gettext_noop("Waits N seconds on connection startup before authentication."),
                  gettext_noop("This allows attaching a debugger to the process."),
                  GUC_NOT_IN_SAMPLE | GUC_UNIT_S
            },
            &PreAuthDelay,
            0, 0, 60, NULL, NULL
      },

      {
            {"checkpoint_segments", PGC_SIGHUP, WAL_CHECKPOINTS,
                  gettext_noop("Sets the maximum distance in log segments between automatic WAL checkpoints."),
                  NULL
            },
            &CheckPointSegments,
            3, 1, INT_MAX, NULL, NULL
      },

      {
            {"checkpoint_timeout", PGC_SIGHUP, WAL_CHECKPOINTS,
                  gettext_noop("Sets the maximum time between automatic WAL checkpoints."),
                  NULL,
                  GUC_UNIT_S
            },
            &CheckPointTimeout,
            300, 30, 3600, NULL, NULL
      },

      {
            {"checkpoint_warning", PGC_SIGHUP, WAL_CHECKPOINTS,
                  gettext_noop("Enables warnings if checkpoint segments are filled more "
                                     "frequently than this."),
                  gettext_noop("Write a message to the server log if checkpoints "
                  "caused by the filling of checkpoint segment files happens more "
                                     "frequently than this number of seconds. Zero turns off the warning."),
                  GUC_UNIT_S
            },
            &CheckPointWarning,
            30, 0, INT_MAX, NULL, NULL
      },

      {
            {"wal_buffers", PGC_POSTMASTER, WAL_SETTINGS,
                  gettext_noop("Sets the number of disk-page buffers in shared memory for WAL."),
                  NULL,
                  GUC_UNIT_XBLOCKS
            },
            &XLOGbuffers,
            8, 4, INT_MAX, NULL, NULL
      },

      {
            {"wal_writer_delay", PGC_SIGHUP, WAL_SETTINGS,
                  gettext_noop("WAL writer sleep time between WAL flushes."),
                  NULL,
                  GUC_UNIT_MS
            },
            &WalWriterDelay,
            200, 1, 10000, NULL, NULL
      },

      {
            {"commit_delay", PGC_USERSET, WAL_SETTINGS,
                  gettext_noop("Sets the delay in microseconds between transaction commit and "
                                     "flushing WAL to disk."),
                  NULL
            },
            &CommitDelay,
            0, 0, 100000, NULL, NULL
      },

      {
            {"commit_siblings", PGC_USERSET, WAL_SETTINGS,
                  gettext_noop("Sets the minimum concurrent open transactions before performing "
                                     "commit_delay."),
                  NULL
            },
            &CommitSiblings,
            5, 1, 1000, NULL, NULL
      },

      {
            {"extra_float_digits", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the number of digits displayed for floating-point values."),
                  gettext_noop("This affects real, double precision, and geometric data types. "
                   "The parameter value is added to the standard number of digits "
                                     "(FLT_DIG or DBL_DIG as appropriate).")
            },
            &extra_float_digits,
            0, -15, 2, NULL, NULL
      },

      {
            {"log_min_duration_statement", PGC_SUSET, LOGGING_WHEN,
                  gettext_noop("Sets the minimum execution time above which "
                                     "statements will be logged."),
                  gettext_noop("Zero prints all queries. -1 turns this feature off."),
                  GUC_UNIT_MS
            },
            &log_min_duration_statement,
            -1, -1, INT_MAX / 1000, NULL, NULL
      },

      {
            {"log_autovacuum_min_duration", PGC_SIGHUP, LOGGING_WHAT,
                  gettext_noop("Sets the minimum execution time above which "
                                     "autovacuum actions will be logged."),
                  gettext_noop("Zero prints all actions. -1 turns autovacuum logging off."),
                  GUC_UNIT_MS
            },
            &Log_autovacuum_min_duration,
            -1, -1, INT_MAX / 1000, NULL, NULL
      },

      {
            {"bgwriter_delay", PGC_SIGHUP, RESOURCES,
                  gettext_noop("Background writer sleep time between rounds."),
                  NULL,
                  GUC_UNIT_MS
            },
            &BgWriterDelay,
            200, 10, 10000, NULL, NULL
      },

      {
            {"bgwriter_lru_maxpages", PGC_SIGHUP, RESOURCES,
                  gettext_noop("Background writer maximum number of LRU pages to flush per round."),
                  NULL
            },
            &bgwriter_lru_maxpages,
            100, 0, 1000, NULL, NULL
      },

      {
            {"effective_io_concurrency",
#ifdef USE_PREFETCH
                  PGC_USERSET,
#else
                  PGC_INTERNAL,
#endif
                  RESOURCES,
                  gettext_noop("Number of simultaneous requests that can be handled efficiently by the disk subsystem."),
                  gettext_noop("For RAID arrays, this should be approximately the number of drive spindles in the array.")
            },
            &effective_io_concurrency,
#ifdef USE_PREFETCH
            1, 0, 1000,
#else
            0, 0, 0,
#endif
            assign_effective_io_concurrency, NULL
      },

      {
            {"log_rotation_age", PGC_SIGHUP, LOGGING_WHERE,
                  gettext_noop("Automatic log file rotation will occur after N minutes."),
                  NULL,
                  GUC_UNIT_MIN
            },
            &Log_RotationAge,
            HOURS_PER_DAY * MINS_PER_HOUR, 0, INT_MAX / MINS_PER_HOUR, NULL, NULL
      },

      {
            {"log_rotation_size", PGC_SIGHUP, LOGGING_WHERE,
                  gettext_noop("Automatic log file rotation will occur after N kilobytes."),
                  NULL,
                  GUC_UNIT_KB
            },
            &Log_RotationSize,
            10 * 1024, 0, INT_MAX / 1024, NULL, NULL
      },

      {
            {"max_function_args", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Shows the maximum number of function arguments."),
                  NULL,
                  GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &max_function_args,
            FUNC_MAX_ARGS, FUNC_MAX_ARGS, FUNC_MAX_ARGS, NULL, NULL
      },

      {
            {"max_index_keys", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Shows the maximum number of index keys."),
                  NULL,
                  GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &max_index_keys,
            INDEX_MAX_KEYS, INDEX_MAX_KEYS, INDEX_MAX_KEYS, NULL, NULL
      },

      {
            {"max_identifier_length", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Shows the maximum identifier length."),
                  NULL,
                  GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &max_identifier_length,
            NAMEDATALEN - 1, NAMEDATALEN - 1, NAMEDATALEN - 1, NULL, NULL
      },

      {
            {"block_size", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Shows the size of a disk block."),
                  NULL,
                  GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &block_size,
            BLCKSZ, BLCKSZ, BLCKSZ, NULL, NULL
      },

      {
            {"segment_size", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Shows the number of pages per disk file."),
                  NULL,
                  GUC_UNIT_BLOCKS | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &segment_size,
            RELSEG_SIZE, RELSEG_SIZE, RELSEG_SIZE, NULL, NULL
      },

      {
            {"wal_block_size", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Shows the block size in the write ahead log."),
                  NULL,
                  GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &wal_block_size,
            XLOG_BLCKSZ, XLOG_BLCKSZ, XLOG_BLCKSZ, NULL, NULL
      },

      {
            {"wal_segment_size", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Shows the number of pages per write ahead log segment."),
                  NULL,
                  GUC_UNIT_XBLOCKS | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &wal_segment_size,
            (XLOG_SEG_SIZE / XLOG_BLCKSZ),
            (XLOG_SEG_SIZE / XLOG_BLCKSZ),
            (XLOG_SEG_SIZE / XLOG_BLCKSZ),
            NULL, NULL
      },

      {
            {"autovacuum_naptime", PGC_SIGHUP, AUTOVACUUM,
                  gettext_noop("Time to sleep between autovacuum runs."),
                  NULL,
                  GUC_UNIT_S
            },
            &autovacuum_naptime,
            60, 1, INT_MAX / 1000, NULL, NULL
      },
      {
            {"autovacuum_vacuum_threshold", PGC_SIGHUP, AUTOVACUUM,
                  gettext_noop("Minimum number of tuple updates or deletes prior to vacuum."),
                  NULL
            },
            &autovacuum_vac_thresh,
            50, 0, INT_MAX, NULL, NULL
      },
      {
            {"autovacuum_analyze_threshold", PGC_SIGHUP, AUTOVACUUM,
                  gettext_noop("Minimum number of tuple inserts, updates or deletes prior to analyze."),
                  NULL
            },
            &autovacuum_anl_thresh,
            50, 0, INT_MAX, NULL, NULL
      },
      {
            /* see varsup.c for why this is PGC_POSTMASTER not PGC_SIGHUP */
            {"autovacuum_freeze_max_age", PGC_POSTMASTER, AUTOVACUUM,
                  gettext_noop("Age at which to autovacuum a table to prevent transaction ID wraparound."),
                  NULL
            },
            &autovacuum_freeze_max_age,
            200000000, 100000000, 2000000000, NULL, NULL
      },
      {
            /* see max_connections */
            {"autovacuum_max_workers", PGC_POSTMASTER, AUTOVACUUM,
                  gettext_noop("Sets the maximum number of simultaneously running autovacuum worker processes."),
                  NULL
            },
            &autovacuum_max_workers,
            3, 1, INT_MAX / 4, assign_autovacuum_max_workers, NULL
      },

      {
            {"tcp_keepalives_idle", PGC_USERSET, CLIENT_CONN_OTHER,
                  gettext_noop("Time between issuing TCP keepalives."),
                  gettext_noop("A value of 0 uses the system default."),
                  GUC_UNIT_S
            },
            &tcp_keepalives_idle,
            0, 0, INT_MAX, assign_tcp_keepalives_idle, show_tcp_keepalives_idle
      },

      {
            {"tcp_keepalives_interval", PGC_USERSET, CLIENT_CONN_OTHER,
                  gettext_noop("Time between TCP keepalive retransmits."),
                  gettext_noop("A value of 0 uses the system default."),
                  GUC_UNIT_S
            },
            &tcp_keepalives_interval,
            0, 0, INT_MAX, assign_tcp_keepalives_interval, show_tcp_keepalives_interval
      },

      {
            {"tcp_keepalives_count", PGC_USERSET, CLIENT_CONN_OTHER,
                  gettext_noop("Maximum number of TCP keepalive retransmits."),
                  gettext_noop("This controls the number of consecutive keepalive retransmits that can be "
                                     "lost before a connection is considered dead. A value of 0 uses the "
                                     "system default."),
            },
            &tcp_keepalives_count,
            0, 0, INT_MAX, assign_tcp_keepalives_count, show_tcp_keepalives_count
      },

      {
            {"gin_fuzzy_search_limit", PGC_USERSET, CLIENT_CONN_OTHER,
                  gettext_noop("Sets the maximum allowed result for exact search by GIN."),
                  NULL,
                  0
            },
            &GinFuzzySearchLimit,
            0, 0, INT_MAX, NULL, NULL
      },

      {
            {"effective_cache_size", PGC_USERSET, QUERY_TUNING_COST,
                  gettext_noop("Sets the planner's assumption about the size of the disk cache."),
                  gettext_noop("That is, the portion of the kernel's disk cache that "
                                     "will be used for PostgreSQL data files. This is measured in disk "
                                     "pages, which are normally 8 kB each."),
                  GUC_UNIT_BLOCKS,
            },
            &effective_cache_size,
            DEFAULT_EFFECTIVE_CACHE_SIZE, 1, INT_MAX, NULL, NULL
      },

      {
            /* Can't be set in postgresql.conf */
            {"server_version_num", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Shows the server version as an integer."),
                  NULL,
                  GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &server_version_num,
            PG_VERSION_NUM, PG_VERSION_NUM, PG_VERSION_NUM, NULL, NULL
      },

      {
            {"log_temp_files", PGC_SUSET, LOGGING_WHAT,
                  gettext_noop("Log the use of temporary files larger than this number of kilobytes."),
                  gettext_noop("Zero logs all files. The default is -1 (turning this feature off)."),
                  GUC_UNIT_KB
            },
            &log_temp_files,
            -1, -1, INT_MAX, NULL, NULL
      },

      {
            {"track_activity_query_size", PGC_POSTMASTER, RESOURCES_MEM,
                  gettext_noop("Sets the size reserved for pg_stat_activity.current_query, in bytes."),
                  NULL,
            },
            &pgstat_track_activity_query_size,
            1024, 100, 102400, NULL, NULL
      },

      /* End-of-list marker */
      {
            {NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL
      }
};


static struct config_real ConfigureNamesReal[] =
{
      {
            {"seq_page_cost", PGC_USERSET, QUERY_TUNING_COST,
                  gettext_noop("Sets the planner's estimate of the cost of a "
                                     "sequentially fetched disk page."),
                  NULL
            },
            &seq_page_cost,
            DEFAULT_SEQ_PAGE_COST, 0, DBL_MAX, NULL, NULL
      },
      {
            {"random_page_cost", PGC_USERSET, QUERY_TUNING_COST,
                  gettext_noop("Sets the planner's estimate of the cost of a "
                                     "nonsequentially fetched disk page."),
                  NULL
            },
            &random_page_cost,
            DEFAULT_RANDOM_PAGE_COST, 0, DBL_MAX, NULL, NULL
      },
      {
            {"cpu_tuple_cost", PGC_USERSET, QUERY_TUNING_COST,
                  gettext_noop("Sets the planner's estimate of the cost of "
                                     "processing each tuple (row)."),
                  NULL
            },
            &cpu_tuple_cost,
            DEFAULT_CPU_TUPLE_COST, 0, DBL_MAX, NULL, NULL
      },
      {
            {"cpu_index_tuple_cost", PGC_USERSET, QUERY_TUNING_COST,
                  gettext_noop("Sets the planner's estimate of the cost of "
                                     "processing each index entry during an index scan."),
                  NULL
            },
            &cpu_index_tuple_cost,
            DEFAULT_CPU_INDEX_TUPLE_COST, 0, DBL_MAX, NULL, NULL
      },
      {
            {"cpu_operator_cost", PGC_USERSET, QUERY_TUNING_COST,
                  gettext_noop("Sets the planner's estimate of the cost of "
                                     "processing each operator or function call."),
                  NULL
            },
            &cpu_operator_cost,
            DEFAULT_CPU_OPERATOR_COST, 0, DBL_MAX, NULL, NULL
      },

      {
            {"cursor_tuple_fraction", PGC_USERSET, QUERY_TUNING_OTHER,
                  gettext_noop("Sets the planner's estimate of the fraction of "
                                     "a cursor's rows that will be retrieved."),
                  NULL
            },
            &cursor_tuple_fraction,
            DEFAULT_CURSOR_TUPLE_FRACTION, 0.0, 1.0, NULL, NULL
      },

      {
            {"geqo_selection_bias", PGC_USERSET, QUERY_TUNING_GEQO,
                  gettext_noop("GEQO: selective pressure within the population."),
                  NULL
            },
            &Geqo_selection_bias,
            DEFAULT_GEQO_SELECTION_BIAS, MIN_GEQO_SELECTION_BIAS,
            MAX_GEQO_SELECTION_BIAS, NULL, NULL
      },

      {
            {"bgwriter_lru_multiplier", PGC_SIGHUP, RESOURCES,
                  gettext_noop("Multiple of the average buffer usage to free per round."),
                  NULL
            },
            &bgwriter_lru_multiplier,
            2.0, 0.0, 10.0, NULL, NULL
      },

      {
            {"seed", PGC_USERSET, UNGROUPED,
                  gettext_noop("Sets the seed for random-number generation."),
                  NULL,
                  GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &phony_random_seed,
            0.0, -1.0, 1.0, assign_random_seed, show_random_seed
      },

      {
            {"autovacuum_vacuum_scale_factor", PGC_SIGHUP, AUTOVACUUM,
                  gettext_noop("Number of tuple updates or deletes prior to vacuum as a fraction of reltuples."),
                  NULL
            },
            &autovacuum_vac_scale,
            0.2, 0.0, 100.0, NULL, NULL
      },
      {
            {"autovacuum_analyze_scale_factor", PGC_SIGHUP, AUTOVACUUM,
                  gettext_noop("Number of tuple inserts, updates or deletes prior to analyze as a fraction of reltuples."),
                  NULL
            },
            &autovacuum_anl_scale,
            0.1, 0.0, 100.0, NULL, NULL
      },

      {
            {"checkpoint_completion_target", PGC_SIGHUP, WAL_CHECKPOINTS,
                  gettext_noop("Time spent flushing dirty buffers during checkpoint, as fraction of checkpoint interval."),
                  NULL
            },
            &CheckPointCompletionTarget,
            0.5, 0.0, 1.0, NULL, NULL
      },

      /* End-of-list marker */
      {
            {NULL, 0, 0, NULL, NULL}, NULL, 0.0, 0.0, 0.0, NULL, NULL
      }
};


static struct config_string ConfigureNamesString[] =
{
      {
            {"archive_command", PGC_SIGHUP, WAL_SETTINGS,
                  gettext_noop("Sets the shell command that will be called to archive a WAL file."),
                  NULL
            },
            &XLogArchiveCommand,
            "", NULL, show_archive_command
      },

      {
            {"client_encoding", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the client's character set encoding."),
                  NULL,
                  GUC_IS_NAME | GUC_REPORT
            },
            &client_encoding_string,
            "SQL_ASCII", assign_client_encoding, NULL
      },

      {
            {"log_line_prefix", PGC_SIGHUP, LOGGING_WHAT,
                  gettext_noop("Controls information prefixed to each log line."),
                  gettext_noop("If blank, no prefix is used.")
            },
            &Log_line_prefix,
            "", NULL, NULL
      },

      {
            {"log_timezone", PGC_SIGHUP, LOGGING_WHAT,
                  gettext_noop("Sets the time zone to use in log messages."),
                  NULL
            },
            &log_timezone_string,
            "UNKNOWN", assign_log_timezone, show_log_timezone
      },

      {
            {"DateStyle", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the display format for date and time values."),
                  gettext_noop("Also controls interpretation of ambiguous "
                                     "date inputs."),
                  GUC_LIST_INPUT | GUC_REPORT
            },
            &datestyle_string,
            "ISO, MDY", assign_datestyle, NULL
      },

      {
            {"default_tablespace", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets the default tablespace to create tables and indexes in."),
                  gettext_noop("An empty string selects the database's default tablespace."),
                  GUC_IS_NAME
            },
            &default_tablespace,
            "", assign_default_tablespace, NULL
      },

      {
            {"temp_tablespaces", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets the tablespace(s) to use for temporary tables and sort files."),
                  NULL,
                  GUC_LIST_INPUT | GUC_LIST_QUOTE
            },
            &temp_tablespaces,
            "", assign_temp_tablespaces, NULL
      },

      {
            {"dynamic_library_path", PGC_SUSET, CLIENT_CONN_OTHER,
                  gettext_noop("Sets the path for dynamically loadable modules."),
                  gettext_noop("If a dynamically loadable module needs to be opened and "
                                     "the specified name does not have a directory component (i.e., the "
                                     "name does not contain a slash), the system will search this path for "
                                     "the specified file."),
                  GUC_SUPERUSER_ONLY
            },
            &Dynamic_library_path,
            "$libdir", NULL, NULL
      },

      {
            {"krb_server_keyfile", PGC_SIGHUP, CONN_AUTH_SECURITY,
                  gettext_noop("Sets the location of the Kerberos server key file."),
                  NULL,
                  GUC_SUPERUSER_ONLY
            },
            &pg_krb_server_keyfile,
            PG_KRB_SRVTAB, NULL, NULL
      },

      {
            {"krb_srvname", PGC_SIGHUP, CONN_AUTH_SECURITY,
                  gettext_noop("Sets the name of the Kerberos service."),
                  NULL
            },
            &pg_krb_srvnam,
            PG_KRB_SRVNAM, NULL, NULL
      },

      {
            {"bonjour_name", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                  gettext_noop("Sets the Bonjour broadcast service name."),
                  NULL
            },
            &bonjour_name,
            "", NULL, NULL
      },

      /* See main.c about why defaults for LC_foo are not all alike */

      {
            {"lc_collate", PGC_INTERNAL, CLIENT_CONN_LOCALE,
                  gettext_noop("Shows the collation order locale."),
                  NULL,
                  GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &locale_collate,
            "C", NULL, NULL
      },

      {
            {"lc_ctype", PGC_INTERNAL, CLIENT_CONN_LOCALE,
                  gettext_noop("Shows the character classification and case conversion locale."),
                  NULL,
                  GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &locale_ctype,
            "C", NULL, NULL
      },

      {
            {"lc_messages", PGC_SUSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the language in which messages are displayed."),
                  NULL
            },
            &locale_messages,
            "", locale_messages_assign, NULL
      },

      {
            {"lc_monetary", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the locale for formatting monetary amounts."),
                  NULL
            },
            &locale_monetary,
            "C", locale_monetary_assign, NULL
      },

      {
            {"lc_numeric", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the locale for formatting numbers."),
                  NULL
            },
            &locale_numeric,
            "C", locale_numeric_assign, NULL
      },

      {
            {"lc_time", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the locale for formatting date and time values."),
                  NULL
            },
            &locale_time,
            "C", locale_time_assign, NULL
      },

      {
            {"shared_preload_libraries", PGC_POSTMASTER, RESOURCES_KERNEL,
                  gettext_noop("Lists shared libraries to preload into server."),
                  NULL,
                  GUC_LIST_INPUT | GUC_LIST_QUOTE | GUC_SUPERUSER_ONLY
            },
            &shared_preload_libraries_string,
            "", NULL, NULL
      },

      {
            {"local_preload_libraries", PGC_BACKEND, CLIENT_CONN_OTHER,
                  gettext_noop("Lists shared libraries to preload into each backend."),
                  NULL,
                  GUC_LIST_INPUT | GUC_LIST_QUOTE
            },
            &local_preload_libraries_string,
            "", NULL, NULL
      },

      {
            {"search_path", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets the schema search order for names that are not schema-qualified."),
                  NULL,
                  GUC_LIST_INPUT | GUC_LIST_QUOTE
            },
            &namespace_search_path,
            "\"$user\",public", assign_search_path, NULL
      },

      {
            /* Can't be set in postgresql.conf */
            {"server_encoding", PGC_INTERNAL, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the server (database) character set encoding."),
                  NULL,
                  GUC_IS_NAME | GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &server_encoding_string,
            "SQL_ASCII", NULL, NULL
      },

      {
            /* Can't be set in postgresql.conf */
            {"server_version", PGC_INTERNAL, PRESET_OPTIONS,
                  gettext_noop("Shows the server version."),
                  NULL,
                  GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &server_version_string,
            PG_VERSION, NULL, NULL
      },

      {
            /* Not for general use --- used by SET ROLE */
            {"role", PGC_USERSET, UNGROUPED,
                  gettext_noop("Sets the current role."),
                  NULL,
                  GUC_IS_NAME | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &role_string,
            "none", assign_role, show_role
      },

      {
            /* Not for general use --- used by SET SESSION AUTHORIZATION */
            {"session_authorization", PGC_USERSET, UNGROUPED,
                  gettext_noop("Sets the session user name."),
                  NULL,
                  GUC_IS_NAME | GUC_REPORT | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &session_authorization_string,
            NULL, assign_session_authorization, show_session_authorization
      },

      {
            {"log_destination", PGC_SIGHUP, LOGGING_WHERE,
                  gettext_noop("Sets the destination for server log output."),
                  gettext_noop("Valid values are combinations of \"stderr\", "
                                     "\"syslog\", \"csvlog\", and \"eventlog\", "
                                     "depending on the platform."),
                  GUC_LIST_INPUT
            },
            &log_destination_string,
            "stderr", assign_log_destination, NULL
      },
      {
            {"log_directory", PGC_SIGHUP, LOGGING_WHERE,
                  gettext_noop("Sets the destination directory for log files."),
                  gettext_noop("Can be specified as relative to the data directory "
                                     "or as absolute path."),
                  GUC_SUPERUSER_ONLY
            },
            &Log_directory,
            "pg_log", assign_canonical_path, NULL
      },
      {
            {"log_filename", PGC_SIGHUP, LOGGING_WHERE,
                  gettext_noop("Sets the file name pattern for log files."),
                  NULL,
                  GUC_SUPERUSER_ONLY
            },
            &Log_filename,
            "postgresql-%Y-%m-%d_%H%M%S.log", NULL, NULL
      },

#ifdef HAVE_SYSLOG
      {
            {"syslog_ident", PGC_SIGHUP, LOGGING_WHERE,
                  gettext_noop("Sets the program name used to identify PostgreSQL "
                                     "messages in syslog."),
                  NULL
            },
            &syslog_ident_str,
            "postgres", assign_syslog_ident, NULL
      },
#endif

      {
            {"TimeZone", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the time zone for displaying and interpreting time stamps."),
                  NULL,
                  GUC_REPORT
            },
            &timezone_string,
            "UNKNOWN", assign_timezone, show_timezone
      },
      {
            {"timezone_abbreviations", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Selects a file of time zone abbreviations."),
                  NULL
            },
            &timezone_abbreviations_string,
            "UNKNOWN", assign_timezone_abbreviations, NULL
      },

      {
            {"transaction_isolation", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets the current transaction's isolation level."),
                  NULL,
                  GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
            },
            &XactIsoLevel_string,
            NULL, assign_XactIsoLevel, show_XactIsoLevel
      },

      {
            {"unix_socket_group", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                  gettext_noop("Sets the owning group of the Unix-domain socket."),
                  gettext_noop("The owning user of the socket is always the user "
                                     "that starts the server.")
            },
            &Unix_socket_group,
            "", NULL, NULL
      },

      {
            {"unix_socket_directory", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                  gettext_noop("Sets the directory where the Unix-domain socket will be created."),
                  NULL,
                  GUC_SUPERUSER_ONLY
            },
            &UnixSocketDir,
            "", assign_canonical_path, NULL
      },

      {
            {"listen_addresses", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
                  gettext_noop("Sets the host name or IP address(es) to listen to."),
                  NULL,
                  GUC_LIST_INPUT
            },
            &ListenAddresses,
            "localhost", NULL, NULL
      },

      {
            {"custom_variable_classes", PGC_SIGHUP, CUSTOM_OPTIONS,
                  gettext_noop("Sets the list of known custom variable classes."),
                  NULL,
                  GUC_LIST_INPUT | GUC_LIST_QUOTE
            },
            &custom_variable_classes,
            NULL, assign_custom_variable_classes, NULL
      },

      {
            {"data_directory", PGC_POSTMASTER, FILE_LOCATIONS,
                  gettext_noop("Sets the server's data directory."),
                  NULL,
                  GUC_SUPERUSER_ONLY
            },
            &data_directory,
            NULL, NULL, NULL
      },

      {
            {"config_file", PGC_POSTMASTER, FILE_LOCATIONS,
                  gettext_noop("Sets the server's main configuration file."),
                  NULL,
                  GUC_DISALLOW_IN_FILE | GUC_SUPERUSER_ONLY
            },
            &ConfigFileName,
            NULL, NULL, NULL
      },

      {
            {"hba_file", PGC_POSTMASTER, FILE_LOCATIONS,
                  gettext_noop("Sets the server's \"hba\" configuration file."),
                  NULL,
                  GUC_SUPERUSER_ONLY
            },
            &HbaFileName,
            NULL, NULL, NULL
      },

      {
            {"ident_file", PGC_POSTMASTER, FILE_LOCATIONS,
                  gettext_noop("Sets the server's \"ident\" configuration file."),
                  NULL,
                  GUC_SUPERUSER_ONLY
            },
            &IdentFileName,
            NULL, NULL, NULL
      },

      {
            {"external_pid_file", PGC_POSTMASTER, FILE_LOCATIONS,
                  gettext_noop("Writes the postmaster PID to the specified file."),
                  NULL,
                  GUC_SUPERUSER_ONLY
            },
            &external_pid_file,
            NULL, assign_canonical_path, NULL
      },

      {
            {"stats_temp_directory", PGC_SIGHUP, STATS_COLLECTOR,
                  gettext_noop("Writes temporary statistics files to the specified directory."),
                  NULL,
                  GUC_SUPERUSER_ONLY
            },
            &pgstat_temp_directory,
            "pg_stat_tmp", assign_pgstat_temp_directory, NULL
      },

      {
            {"default_text_search_config", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets default text search configuration."),
                  NULL
            },
            &TSCurrentConfig,
            "pg_catalog.simple", assignTSCurrentConfig, NULL
      },

#ifdef USE_SSL
      {
            {"ssl_ciphers", PGC_POSTMASTER, CONN_AUTH_SECURITY,
                  gettext_noop("Sets the list of allowed SSL ciphers."),
                  NULL,
                  GUC_SUPERUSER_ONLY
            },
            &SSLCipherSuites,
            "ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH", NULL, NULL
      },
#endif   /* USE_SSL */

      /* End-of-list marker */
      {
            {NULL, 0, 0, NULL, NULL}, NULL, NULL, NULL, NULL
      }
};


static struct config_enum ConfigureNamesEnum[] =
{
      {
            {"backslash_quote", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                  gettext_noop("Sets whether \"\\'\" is allowed in string literals."),
                  NULL
            },
            &backslash_quote,
            BACKSLASH_QUOTE_SAFE_ENCODING, backslash_quote_options, NULL, NULL
      },

      {
            {"client_min_messages", PGC_USERSET, LOGGING_WHEN,
                  gettext_noop("Sets the message levels that are sent to the client."),
                  gettext_noop("Each level includes all the levels that follow it. The later"
                                     " the level, the fewer messages are sent.")
            },
            &client_min_messages,
            NOTICE, client_message_level_options, NULL, NULL
      },

      {
            {"constraint_exclusion", PGC_USERSET, QUERY_TUNING_OTHER,
                  gettext_noop("Enables the planner to use constraints to optimize queries."),
                  gettext_noop("Table scans will be skipped if their constraints"
                                     " guarantee that no rows match the query.")
            },
            &constraint_exclusion,
            CONSTRAINT_EXCLUSION_PARTITION, constraint_exclusion_options,
            NULL, NULL
      },

      {
            {"default_transaction_isolation", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets the transaction isolation level of each new transaction."),
                  NULL
            },
            &DefaultXactIsoLevel,
            XACT_READ_COMMITTED, isolation_level_options, NULL, NULL
      },

      {
            {"IntervalStyle", PGC_USERSET, CLIENT_CONN_LOCALE,
                  gettext_noop("Sets the display format for interval values."),
                  NULL,
                  GUC_REPORT
            },
            &IntervalStyle,
            INTSTYLE_POSTGRES, intervalstyle_options, NULL, NULL
      },

      {
            {"log_error_verbosity", PGC_SUSET, LOGGING_WHEN,
                  gettext_noop("Sets the verbosity of logged messages."),
                  NULL
            },
            &Log_error_verbosity,
            PGERROR_DEFAULT, log_error_verbosity_options, NULL, NULL
      },

      {
            {"log_min_messages", PGC_SUSET, LOGGING_WHEN,
                  gettext_noop("Sets the message levels that are logged."),
                  gettext_noop("Each level includes all the levels that follow it. The later"
                                     " the level, the fewer messages are sent.")
            },
            &log_min_messages,
            WARNING, server_message_level_options, NULL, NULL
      },

      {
            {"log_min_error_statement", PGC_SUSET, LOGGING_WHEN,
                  gettext_noop("Causes all statements generating error at or above this level to be logged."),
                  gettext_noop("Each level includes all the levels that follow it. The later"
                                     " the level, the fewer messages are sent.")
            },
            &log_min_error_statement,
            ERROR, server_message_level_options, NULL, NULL
      },

      {
            {"log_statement", PGC_SUSET, LOGGING_WHAT,
                  gettext_noop("Sets the type of statements logged."),
                  NULL
            },
            &log_statement,
            LOGSTMT_NONE, log_statement_options, NULL, NULL
      },

#ifdef HAVE_SYSLOG
      {
            {"syslog_facility", PGC_SIGHUP, LOGGING_WHERE,
                  gettext_noop("Sets the syslog \"facility\" to be used when syslog enabled."),
                  NULL
            },
            &syslog_facility,
            LOG_LOCAL0, syslog_facility_options, assign_syslog_facility, NULL
      },
#endif

      {
            {"regex_flavor", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
                  gettext_noop("Sets the regular expression \"flavor\"."),
                  NULL
            },
            &regex_flavor,
            REG_ADVANCED, regex_flavor_options, NULL, NULL
      },

      {
            {"session_replication_role", PGC_SUSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets the session's behavior for triggers and rewrite rules."),
                  NULL
            },
            &SessionReplicationRole,
            SESSION_REPLICATION_ROLE_ORIGIN, session_replication_role_options,
            assign_session_replication_role, NULL
      },

      {
            {"track_functions", PGC_SUSET, STATS_COLLECTOR,
                  gettext_noop("Collects function-level statistics on database activity."),
                  NULL
            },
            &pgstat_track_functions,
            TRACK_FUNC_OFF, track_function_options, NULL, NULL
      },

      {
            {"wal_sync_method", PGC_SIGHUP, WAL_SETTINGS,
                  gettext_noop("Selects the method used for forcing WAL updates to disk."),
                  NULL
            },
            &sync_method,
            DEFAULT_SYNC_METHOD, sync_method_options,
            assign_xlog_sync_method, NULL
      },

      {
            {"xmlbinary", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets how binary values are to be encoded in XML."),
                  NULL
            },
            &xmlbinary,
            XMLBINARY_BASE64, xmlbinary_options, NULL, NULL
      },

      {
            {"xmloption", PGC_USERSET, CLIENT_CONN_STATEMENT,
                  gettext_noop("Sets whether XML data in implicit parsing and serialization "
                                     "operations is to be considered as documents or content fragments."),
                  NULL
            },
            &xmloption,
            XMLOPTION_CONTENT, xmloption_options, NULL, NULL
      },


      /* End-of-list marker */
      {
            {NULL, 0, 0, NULL, NULL}, NULL, 0, NULL, NULL, NULL
      }
};

/******** end of options list ********/


/*
 * To allow continued support of obsolete names for GUC variables, we apply
 * the following mappings to any unrecognized name.  Note that an old name
 * should be mapped to a new one only if the new variable has very similar
 * semantics to the old.
 */
static const char *const map_old_guc_names[] = {
      "sort_mem", "work_mem",
      "vacuum_mem", "maintenance_work_mem",
      NULL
};


/*
 * Actual lookup of variables is done through this single, sorted array.
 */
static struct config_generic **guc_variables;

/* Current number of variables contained in the vector */
static int  num_guc_variables;

/* Vector capacity */
static int  size_guc_variables;


static bool guc_dirty;              /* TRUE if need to do commit/abort work */

static bool reporting_enabled;      /* TRUE to enable GUC_REPORT */

static int  GUCNestLevel = 0; /* 1 when in main transaction */


static int  guc_var_compare(const void *a, const void *b);
static int  guc_name_compare(const char *namea, const char *nameb);
static void InitializeOneGUCOption(struct config_generic * gconf);
static void push_old_value(struct config_generic * gconf, GucAction action);
static void ReportGUCOption(struct config_generic * record);
static void ShowGUCConfigOption(const char *name, DestReceiver *dest);
static void ShowAllGUCConfig(DestReceiver *dest);
static char *_ShowOption(struct config_generic * record, bool use_units);
static bool is_newvalue_equal(struct config_generic * record, const char *newvalue);


/*
 * Some infrastructure for checking malloc/strdup/realloc calls
 */
static void *
guc_malloc(int elevel, size_t size)
{
      void     *data;

      data = malloc(size);
      if (data == NULL)
            ereport(elevel,
                        (errcode(ERRCODE_OUT_OF_MEMORY),
                         errmsg("out of memory")));
      return data;
}

static void *
guc_realloc(int elevel, void *old, size_t size)
{
      void     *data;

      data = realloc(old, size);
      if (data == NULL)
            ereport(elevel,
                        (errcode(ERRCODE_OUT_OF_MEMORY),
                         errmsg("out of memory")));
      return data;
}

static char *
guc_strdup(int elevel, const char *src)
{
      char     *data;

      data = strdup(src);
      if (data == NULL)
            ereport(elevel,
                        (errcode(ERRCODE_OUT_OF_MEMORY),
                         errmsg("out of memory")));
      return data;
}


/*
 * Support for assigning to a field of a string GUC item.  Free the prior
 * value if it's not referenced anywhere else in the item (including stacked
 * states).
 */
static void
set_string_field(struct config_string * conf, char **field, char *newval)
{
      char     *oldval = *field;
      GucStack   *stack;

      /* Do the assignment */
      *field = newval;

      /* Exit if any duplicate references, or if old value was NULL anyway */
      if (oldval == NULL ||
            oldval == *(conf->variable) ||
            oldval == conf->reset_val ||
            oldval == conf->boot_val)
            return;
      for (stack = conf->gen.stack; stack; stack = stack->prev)
      {
            if (oldval == stack->prior.stringval ||
                  oldval == stack->masked.stringval)
                  return;
      }

      /* Not used anymore, so free it */
      free(oldval);
}

/*
 * Detect whether strval is referenced anywhere in a GUC string item
 */
static bool
string_field_used(struct config_string * conf, char *strval)
{
      GucStack   *stack;

      if (strval == *(conf->variable) ||
            strval == conf->reset_val ||
            strval == conf->boot_val)
            return true;
      for (stack = conf->gen.stack; stack; stack = stack->prev)
      {
            if (strval == stack->prior.stringval ||
                  strval == stack->masked.stringval)
                  return true;
      }
      return false;
}

/*
 * Support for copying a variable's active value into a stack entry
 */
static void
set_stack_value(struct config_generic * gconf, union config_var_value * val)
{
      switch (gconf->vartype)
      {
            case PGC_BOOL:
                  val->boolval =
                        *((struct config_bool *) gconf)->variable;
                  break;
            case PGC_INT:
                  val->intval =
                        *((struct config_int *) gconf)->variable;
                  break;
            case PGC_REAL:
                  val->realval =
                        *((struct config_real *) gconf)->variable;
                  break;
            case PGC_STRING:
                  /* we assume stringval is NULL if not valid */
                  set_string_field((struct config_string *) gconf,
                                           &(val->stringval),
                                           *((struct config_string *) gconf)->variable);
                  break;
            case PGC_ENUM:
                  val->enumval =
                        *((struct config_enum *) gconf)->variable;
                  break;
      }
}

/*
 * Support for discarding a no-longer-needed value in a stack entry
 */
static void
discard_stack_value(struct config_generic * gconf, union config_var_value * val)
{
      switch (gconf->vartype)
      {
            case PGC_BOOL:
            case PGC_INT:
            case PGC_REAL:
            case PGC_ENUM:
                  /* no need to do anything */
                  break;
            case PGC_STRING:
                  set_string_field((struct config_string *) gconf,
                                           &(val->stringval),
                                           NULL);
                  break;
      }
}


/*
 * Fetch the sorted array pointer (exported for help_config.c's use ONLY)
 */
struct config_generic **
get_guc_variables(void)
{
      return guc_variables;
}


/*
 * Build the sorted array.    This is split out so that it could be
 * re-executed after startup (eg, we could allow loadable modules to
 * add vars, and then we'd need to re-sort).
 */
void
build_guc_variables(void)
{
      int               size_vars;
      int               num_vars = 0;
      struct config_generic **guc_vars;
      int               i;

      for (i = 0; ConfigureNamesBool[i].gen.name; i++)
      {
            struct config_bool *conf = &ConfigureNamesBool[i];

            /* Rather than requiring vartype to be filled in by hand, do this: */
            conf->gen.vartype = PGC_BOOL;
            num_vars++;
      }

      for (i = 0; ConfigureNamesInt[i].gen.name; i++)
      {
            struct config_int *conf = &ConfigureNamesInt[i];

            conf->gen.vartype = PGC_INT;
            num_vars++;
      }

      for (i = 0; ConfigureNamesReal[i].gen.name; i++)
      {
            struct config_real *conf = &ConfigureNamesReal[i];

            conf->gen.vartype = PGC_REAL;
            num_vars++;
      }

      for (i = 0; ConfigureNamesString[i].gen.name; i++)
      {
            struct config_string *conf = &ConfigureNamesString[i];

            conf->gen.vartype = PGC_STRING;
            num_vars++;
      }

      for (i = 0; ConfigureNamesEnum[i].gen.name; i++)
      {
            struct config_enum *conf = &ConfigureNamesEnum[i];

            conf->gen.vartype = PGC_ENUM;
            num_vars++;
      }

      /*
       * Create table with 20% slack
       */
      size_vars = num_vars + num_vars / 4;

      guc_vars = (struct config_generic **)
            guc_malloc(FATAL, size_vars * sizeof(struct config_generic *));

      num_vars = 0;

      for (i = 0; ConfigureNamesBool[i].gen.name; i++)
            guc_vars[num_vars++] = &ConfigureNamesBool[i].gen;

      for (i = 0; ConfigureNamesInt[i].gen.name; i++)
            guc_vars[num_vars++] = &ConfigureNamesInt[i].gen;

      for (i = 0; ConfigureNamesReal[i].gen.name; i++)
            guc_vars[num_vars++] = &ConfigureNamesReal[i].gen;

      for (i = 0; ConfigureNamesString[i].gen.name; i++)
            guc_vars[num_vars++] = &ConfigureNamesString[i].gen;

      for (i = 0; ConfigureNamesEnum[i].gen.name; i++)
            guc_vars[num_vars++] = &ConfigureNamesEnum[i].gen;

      if (guc_variables)
            free(guc_variables);
      guc_variables = guc_vars;
      num_guc_variables = num_vars;
      size_guc_variables = size_vars;
      qsort((void *) guc_variables, num_guc_variables,
              sizeof(struct config_generic *), guc_var_compare);
}

/*
 * Add a new GUC variable to the list of known variables. The
 * list is expanded if needed.
 */
static bool
add_guc_variable(struct config_generic * var, int elevel)
{
      if (num_guc_variables + 1 >= size_guc_variables)
      {
            /*
             * Increase the vector by 25%
             */
            int               size_vars = size_guc_variables + size_guc_variables / 4;
            struct config_generic **guc_vars;

            if (size_vars == 0)
            {
                  size_vars = 100;
                  guc_vars = (struct config_generic **)
                        guc_malloc(elevel, size_vars * sizeof(struct config_generic *));
            }
            else
            {
                  guc_vars = (struct config_generic **)
                        guc_realloc(elevel, guc_variables, size_vars * sizeof(struct config_generic *));
            }

            if (guc_vars == NULL)
                  return false;           /* out of memory */

            guc_variables = guc_vars;
            size_guc_variables = size_vars;
      }
      guc_variables[num_guc_variables++] = var;
      qsort((void *) guc_variables, num_guc_variables,
              sizeof(struct config_generic *), guc_var_compare);
      return true;
}

/*
 * Create and add a placeholder variable. It's presumed to belong
 * to a valid custom variable class at this point.
 */
static struct config_generic *
add_placeholder_variable(const char *name, int elevel)
{
      size_t            sz = sizeof(struct config_string) + sizeof(char *);
      struct config_string *var;
      struct config_generic *gen;

      var = (struct config_string *) guc_malloc(elevel, sz);
      if (var == NULL)
            return NULL;
      memset(var, 0, sz);
      gen = &var->gen;

      gen->name = guc_strdup(elevel, name);
      if (gen->name == NULL)
      {
            free(var);
            return NULL;
      }

      gen->context = PGC_USERSET;
      gen->group = CUSTOM_OPTIONS;
      gen->short_desc = "GUC placeholder variable";
      gen->flags = GUC_NO_SHOW_ALL | GUC_NOT_IN_SAMPLE | GUC_CUSTOM_PLACEHOLDER;
      gen->vartype = PGC_STRING;

      /*
       * The char* is allocated at the end of the struct since we have no
       * 'static' place to point to.      Note that the current value, as well as
       * the boot and reset values, start out NULL.
       */
      var->variable = (char **) (var + 1);

      if (!add_guc_variable((struct config_generic *) var, elevel))
      {
            free((void *) gen->name);
            free(var);
            return NULL;
      }

      return gen;
}

/*
 * Detect whether the portion of "name" before dotPos matches any custom
 * variable class name listed in custom_var_classes.  The latter must be
 * formatted the way that assign_custom_variable_classes does it, ie,
 * no whitespace.  NULL is valid for custom_var_classes.
 */
static bool
is_custom_class(const char *name, int dotPos, const char *custom_var_classes)
{
      bool        result = false;
      const char *ccs = custom_var_classes;

      if (ccs != NULL)
      {
            const char *start = ccs;

            for (;; ++ccs)
            {
                  char        c = *ccs;

                  if (c == '\0' || c == ',')
                  {
                        if (dotPos == ccs - start && strncmp(start, name, dotPos) == 0)
                        {
                              result = true;
                              break;
                        }
                        if (c == '\0')
                              break;
                        start = ccs + 1;
                  }
            }
      }
      return result;
}

/*
 * Look up option NAME.  If it exists, return a pointer to its record,
 * else return NULL.  If create_placeholders is TRUE, we'll create a
 * placeholder record for a valid-looking custom variable name.
 */
static struct config_generic *
find_option(const char *name, bool create_placeholders, int elevel)
{
      const char **key = &name;
      struct config_generic **res;
      int               i;

      Assert(name);

      /*
       * By equating const char ** with struct config_generic *, we are assuming
       * the name field is first in config_generic.
       */
      res = (struct config_generic **) bsearch((void *) &key,
                                                                   (void *) guc_variables,
                                                                   num_guc_variables,
                                                                   sizeof(struct config_generic *),
                                                                   guc_var_compare);
      if (res)
            return *res;

      /*
       * See if the name is an obsolete name for a variable.      We assume that the
       * set of supported old names is short enough that a brute-force search is
       * the best way.
       */
      for (i = 0; map_old_guc_names[i] != NULL; i += 2)
      {
            if (guc_name_compare(name, map_old_guc_names[i]) == 0)
                  return find_option(map_old_guc_names[i + 1], false, elevel);
      }

      if (create_placeholders)
      {
            /*
             * Check if the name is qualified, and if so, check if the qualifier
             * matches any custom variable class.  If so, add a placeholder.
             */
            const char *dot = strchr(name, GUC_QUALIFIER_SEPARATOR);

            if (dot != NULL &&
                  is_custom_class(name, dot - name, custom_variable_classes))
                  return add_placeholder_variable(name, elevel);
      }

      /* Unknown name */
      return NULL;
}


/*
 * comparator for qsorting and bsearching guc_variables array
 */
static int
guc_var_compare(const void *a, const void *b)
{
      struct config_generic *confa = *(struct config_generic **) a;
      struct config_generic *confb = *(struct config_generic **) b;

      return guc_name_compare(confa->name, confb->name);
}

/*
 * the bare comparison function for GUC names
 */
static int
guc_name_compare(const char *namea, const char *nameb)
{
      /*
       * The temptation to use strcasecmp() here must be resisted, because the
       * array ordering has to remain stable across setlocale() calls. So, build
       * our own with a simple ASCII-only downcasing.
       */
      while (*namea && *nameb)
      {
            char        cha = *namea++;
            char        chb = *nameb++;

            if (cha >= 'A' && cha <= 'Z')
                  cha += 'a' - 'A';
            if (chb >= 'A' && chb <= 'Z')
                  chb += 'a' - 'A';
            if (cha != chb)
                  return cha - chb;
      }
      if (*namea)
            return 1;                     /* a is longer */
      if (*nameb)
            return -1;                    /* b is longer */
      return 0;
}


/*
 * Initialize GUC options during program startup.
 *
 * Note that we cannot read the config file yet, since we have not yet
 * processed command-line switches.
 */
void
InitializeGUCOptions(void)
{
      int               i;
      char     *env;
      long        stack_rlimit;

      /*
       * Before log_line_prefix could possibly receive a nonempty setting, make
       * sure that timezone processing is minimally alive (see elog.c).
       */
      pg_timezone_pre_initialize();

      /*
       * Build sorted array of all GUC variables.
       */
      build_guc_variables();

      /*
       * Load all variables with their compiled-in defaults, and initialize
       * status fields as needed.
       */
      for (i = 0; i < num_guc_variables; i++)
      {
            InitializeOneGUCOption(guc_variables[i]);
      }

      guc_dirty = false;

      reporting_enabled = false;

      /*
       * Prevent any attempt to override the transaction modes from
       * non-interactive sources.
       */
      SetConfigOption("transaction_isolation", "default",
                              PGC_POSTMASTER, PGC_S_OVERRIDE);
      SetConfigOption("transaction_read_only", "no",
                              PGC_POSTMASTER, PGC_S_OVERRIDE);

      /*
       * For historical reasons, some GUC parameters can receive defaults from
       * environment variables.  Process those settings.    NB: if you add or
       * remove anything here, see also ProcessConfigFile().
       */

      env = getenv("PGPORT");
      if (env != NULL)
            SetConfigOption("port", env, PGC_POSTMASTER, PGC_S_ENV_VAR);

      env = getenv("PGDATESTYLE");
      if (env != NULL)
            SetConfigOption("datestyle", env, PGC_POSTMASTER, PGC_S_ENV_VAR);

      env = getenv("PGCLIENTENCODING");
      if (env != NULL)
            SetConfigOption("client_encoding", env, PGC_POSTMASTER, PGC_S_ENV_VAR);

      /*
       * rlimit isn't exactly an "environment variable", but it behaves about
       * the same.  If we can identify the platform stack depth rlimit, increase
       * default stack depth setting up to whatever is safe (but at most 2MB).
       */
      stack_rlimit = get_stack_depth_rlimit();
      if (stack_rlimit > 0)
      {
            int               new_limit = (stack_rlimit - STACK_DEPTH_SLOP) / 1024L;

            if (new_limit > 100)
            {
                  char        limbuf[16];

                  new_limit = Min(new_limit, 2048);
                  sprintf(limbuf, "%d", new_limit);
                  SetConfigOption("max_stack_depth", limbuf,
                                          PGC_POSTMASTER, PGC_S_ENV_VAR);
            }
      }
}

/*
 * Initialize one GUC option variable to its compiled-in default.
 */
static void
InitializeOneGUCOption(struct config_generic * gconf)
{
      gconf->status = 0;
      gconf->reset_source = PGC_S_DEFAULT;
      gconf->source = PGC_S_DEFAULT;
      gconf->stack = NULL;
      gconf->sourcefile = NULL;
      gconf->sourceline = 0;

      switch (gconf->vartype)
      {
            case PGC_BOOL:
                  {
                        struct config_bool *conf = (struct config_bool *) gconf;

                        if (conf->assign_hook)
                              if (!(*conf->assign_hook) (conf->boot_val, true,
                                                                     PGC_S_DEFAULT))
                                    elog(FATAL, "failed to initialize %s to %d",
                                           conf->gen.name, (int) conf->boot_val);
                        *conf->variable = conf->reset_val = conf->boot_val;
                        break;
                  }
            case PGC_INT:
                  {
                        struct config_int *conf = (struct config_int *) gconf;

                        Assert(conf->boot_val >= conf->min);
                        Assert(conf->boot_val <= conf->max);
                        if (conf->assign_hook)
                              if (!(*conf->assign_hook) (conf->boot_val, true,
                                                                     PGC_S_DEFAULT))
                                    elog(FATAL, "failed to initialize %s to %d",
                                           conf->gen.name, conf->boot_val);
                        *conf->variable = conf->reset_val = conf->boot_val;
                        break;
                  }
            case PGC_REAL:
                  {
                        struct config_real *conf = (struct config_real *) gconf;

                        Assert(conf->boot_val >= conf->min);
                        Assert(conf->boot_val <= conf->max);
                        if (conf->assign_hook)
                              if (!(*conf->assign_hook) (conf->boot_val, true,
                                                                     PGC_S_DEFAULT))
                                    elog(FATAL, "failed to initialize %s to %g",
                                           conf->gen.name, conf->boot_val);
                        *conf->variable = conf->reset_val = conf->boot_val;
                        break;
                  }
            case PGC_STRING:
                  {
                        struct config_string *conf = (struct config_string *) gconf;
                        char     *str;

                        *conf->variable = NULL;
                        conf->reset_val = NULL;

                        if (conf->boot_val == NULL)
                        {
                              /* leave the value NULL, do not call assign hook */
                              break;
                        }

                        str = guc_strdup(FATAL, conf->boot_val);
                        conf->reset_val = str;

                        if (conf->assign_hook)
                        {
                              const char *newstr;

                              newstr = (*conf->assign_hook) (str, true,
                                                                           PGC_S_DEFAULT);
                              if (newstr == NULL)
                              {
                                    elog(FATAL, "failed to initialize %s to \"%s\"",
                                           conf->gen.name, str);
                              }
                              else if (newstr != str)
                              {
                                    free(str);

                                    /*
                                     * See notes in set_config_option about casting
                                     */
                                    str = (char *) newstr;
                                    conf->reset_val = str;
                              }
                        }
                        *conf->variable = str;
                        break;
                  }
            case PGC_ENUM:
                  {
                        struct config_enum *conf = (struct config_enum *) gconf;

                        if (conf->assign_hook)
                              if (!(*conf->assign_hook) (conf->boot_val, true,
                                                                     PGC_S_DEFAULT))
                                    elog(FATAL, "failed to initialize %s to %s",
                                           conf->gen.name,
                                      config_enum_lookup_by_value(conf, conf->boot_val));
                        *conf->variable = conf->reset_val = conf->boot_val;
                        break;
                  }
      }
}


/*
 * Select the configuration files and data directory to be used, and
 * do the initial read of postgresql.conf.
 *
 * This is called after processing command-line switches.
 *          userDoption is the -D switch value if any (NULL if unspecified).
 *          progname is just for use in error messages.
 *
 * Returns true on success; on failure, prints a suitable error message
 * to stderr and returns false.
 */
bool
SelectConfigFiles(const char *userDoption, const char *progname)
{
      char     *configdir;
      char     *fname;
      struct stat stat_buf;

      /* configdir is -D option, or $PGDATA if no -D */
      if (userDoption)
            configdir = make_absolute_path(userDoption);
      else
            configdir = make_absolute_path(getenv("PGDATA"));

      /*
       * Find the configuration file: if config_file was specified on the
       * command line, use it, else use configdir/postgresql.conf.  In any case
       * ensure the result is an absolute path, so that it will be interpreted
       * the same way by future backends.
       */
      if (ConfigFileName)
            fname = make_absolute_path(ConfigFileName);
      else if (configdir)
      {
            fname = guc_malloc(FATAL,
                                       strlen(configdir) + strlen(CONFIG_FILENAME) + 2);
            sprintf(fname, "%s/%s", configdir, CONFIG_FILENAME);
      }
      else
      {
            write_stderr("%s does not know where to find the server configuration file.\n"
                               "You must specify the --config-file or -D invocation "
                               "option or set the PGDATA environment variable.\n",
                               progname);
            return false;
      }

      /*
       * Set the ConfigFileName GUC variable to its final value, ensuring that
       * it can't be overridden later.
       */
      SetConfigOption("config_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
      free(fname);

      /*
       * Now read the config file for the first time.
       */
      if (stat(ConfigFileName, &stat_buf) != 0)
      {
            write_stderr("%s cannot access the server configuration file \"%s\": %s\n",
                               progname, ConfigFileName, strerror(errno));
            return false;
      }

      ProcessConfigFile(PGC_POSTMASTER);

      /*
       * If the data_directory GUC variable has been set, use that as DataDir;
       * otherwise use configdir if set; else punt.
       *
       * Note: SetDataDir will copy and absolute-ize its argument, so we don't
       * have to.
       */
      if (data_directory)
            SetDataDir(data_directory);
      else if (configdir)
            SetDataDir(configdir);
      else
      {
            write_stderr("%s does not know where to find the database system data.\n"
                               "This can be specified as \"data_directory\" in \"%s\", "
                               "or by the -D invocation option, or by the "
                               "PGDATA environment variable.\n",
                               progname, ConfigFileName);
            return false;
      }

      /*
       * Reflect the final DataDir value back into the data_directory GUC var.
       * (If you are wondering why we don't just make them a single variable,
       * it's because the EXEC_BACKEND case needs DataDir to be transmitted to
       * child backends specially.  XXX is that still true?  Given that we now
       * chdir to DataDir, EXEC_BACKEND can read the config file without knowing
       * DataDir in advance.)
       */
      SetConfigOption("data_directory", DataDir, PGC_POSTMASTER, PGC_S_OVERRIDE);

      /*
       * Figure out where pg_hba.conf is, and make sure the path is absolute.
       */
      if (HbaFileName)
            fname = make_absolute_path(HbaFileName);
      else if (configdir)
      {
            fname = guc_malloc(FATAL,
                                       strlen(configdir) + strlen(HBA_FILENAME) + 2);
            sprintf(fname, "%s/%s", configdir, HBA_FILENAME);
      }
      else
      {
            write_stderr("%s does not know where to find the \"hba\" configuration file.\n"
                               "This can be specified as \"hba_file\" in \"%s\", "
                               "or by the -D invocation option, or by the "
                               "PGDATA environment variable.\n",
                               progname, ConfigFileName);
            return false;
      }
      SetConfigOption("hba_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
      free(fname);

      /*
       * Likewise for pg_ident.conf.
       */
      if (IdentFileName)
            fname = make_absolute_path(IdentFileName);
      else if (configdir)
      {
            fname = guc_malloc(FATAL,
                                       strlen(configdir) + strlen(IDENT_FILENAME) + 2);
            sprintf(fname, "%s/%s", configdir, IDENT_FILENAME);
      }
      else
      {
            write_stderr("%s does not know where to find the \"ident\" configuration file.\n"
                               "This can be specified as \"ident_file\" in \"%s\", "
                               "or by the -D invocation option, or by the "
                               "PGDATA environment variable.\n",
                               progname, ConfigFileName);
            return false;
      }
      SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
      free(fname);

      free(configdir);

      return true;
}


/*
 * Reset all options to their saved default values (implements RESET ALL)
 */
void
ResetAllOptions(void)
{
      int               i;

      for (i = 0; i < num_guc_variables; i++)
      {
            struct config_generic *gconf = guc_variables[i];

            /* Don't reset non-SET-able values */
            if (gconf->context != PGC_SUSET &&
                  gconf->context != PGC_USERSET)
                  continue;
            /* Don't reset if special exclusion from RESET ALL */
            if (gconf->flags & GUC_NO_RESET_ALL)
                  continue;
            /* No need to reset if wasn't SET */
            if (gconf->source <= PGC_S_OVERRIDE)
                  continue;

            /* Save old value to support transaction abort */
            push_old_value(gconf, GUC_ACTION_SET);

            switch (gconf->vartype)
            {
                  case PGC_BOOL:
                        {
                              struct config_bool *conf = (struct config_bool *) gconf;

                              if (conf->assign_hook)
                                    if (!(*conf->assign_hook) (conf->reset_val, true,
                                                                           PGC_S_SESSION))
                                          elog(ERROR, "failed to reset %s to %d",
                                                 conf->gen.name, (int) conf->reset_val);
                              *conf->variable = conf->reset_val;
                              break;
                        }
                  case PGC_INT:
                        {
                              struct config_int *conf = (struct config_int *) gconf;

                              if (conf->assign_hook)
                                    if (!(*conf->assign_hook) (conf->reset_val, true,
                                                                           PGC_S_SESSION))
                                          elog(ERROR, "failed to reset %s to %d",
                                                 conf->gen.name, conf->reset_val);
                              *conf->variable = conf->reset_val;
                              break;
                        }
                  case PGC_REAL:
                        {
                              struct config_real *conf = (struct config_real *) gconf;

                              if (conf->assign_hook)
                                    if (!(*conf->assign_hook) (conf->reset_val, true,
                                                                           PGC_S_SESSION))
                                          elog(ERROR, "failed to reset %s to %g",
                                                 conf->gen.name, conf->reset_val);
                              *conf->variable = conf->reset_val;
                              break;
                        }
                  case PGC_STRING:
                        {
                              struct config_string *conf = (struct config_string *) gconf;
                              char     *str;

                              /* We need not strdup here */
                              str = conf->reset_val;

                              if (conf->assign_hook && str)
                              {
                                    const char *newstr;

                                    newstr = (*conf->assign_hook) (str, true,
                                                                                 PGC_S_SESSION);
                                    if (newstr == NULL)
                                          elog(ERROR, "failed to reset %s to \"%s\"",
                                                 conf->gen.name, str);
                                    else if (newstr != str)
                                    {
                                          /*
                                           * See notes in set_config_option about casting
                                           */
                                          str = (char *) newstr;
                                    }
                              }

                              set_string_field(conf, conf->variable, str);
                              break;
                        }
                  case PGC_ENUM:
                        {
                              struct config_enum *conf = (struct config_enum *) gconf;

                              if (conf->assign_hook)
                                    if (!(*conf->assign_hook) (conf->reset_val, true,
                                                                           PGC_S_SESSION))
                                          elog(ERROR, "failed to reset %s to %s",
                                                 conf->gen.name,
                                                 config_enum_lookup_by_value(conf, conf->reset_val));
                              *conf->variable = conf->reset_val;
                              break;
                        }
            }

            gconf->source = gconf->reset_source;

            if (gconf->flags & GUC_REPORT)
                  ReportGUCOption(gconf);
      }
}


/*
 * push_old_value
 *          Push previous state during transactional assignment to a GUC variable.
 */
static void
push_old_value(struct config_generic * gconf, GucAction action)
{
      GucStack   *stack;

      /* If we're not inside a nest level, do nothing */
      if (GUCNestLevel == 0)
            return;

      /* Do we already have a stack entry of the current nest level? */
      stack = gconf->stack;
      if (stack && stack->nest_level >= GUCNestLevel)
      {
            /* Yes, so adjust its state if necessary */
            Assert(stack->nest_level == GUCNestLevel);
            switch (action)
            {
                  case GUC_ACTION_SET:
                        /* SET overrides any prior action at same nest level */
                        if (stack->state == GUC_SET_LOCAL)
                        {
                              /* must discard old masked value */
                              discard_stack_value(gconf, &stack->masked);
                        }
                        stack->state = GUC_SET;
                        break;
                  case GUC_ACTION_LOCAL:
                        if (stack->state == GUC_SET)
                        {
                              /* SET followed by SET LOCAL, remember SET's value */
                              set_stack_value(gconf, &stack->masked);
                              stack->state = GUC_SET_LOCAL;
                        }
                        /* in all other cases, no change to stack entry */
                        break;
                  case GUC_ACTION_SAVE:
                        /* Could only have a prior SAVE of same variable */
                        Assert(stack->state == GUC_SAVE);
                        break;
            }
            Assert(guc_dirty);            /* must be set already */
            return;
      }

      /*
       * Push a new stack entry
       *
       * We keep all the stack entries in TopTransactionContext for simplicity.
       */
      stack = (GucStack *) MemoryContextAllocZero(TopTransactionContext,
                                                                        sizeof(GucStack));

      stack->prev = gconf->stack;
      stack->nest_level = GUCNestLevel;
      switch (action)
      {
            case GUC_ACTION_SET:
                  stack->state = GUC_SET;
                  break;
            case GUC_ACTION_LOCAL:
                  stack->state = GUC_LOCAL;
                  break;
            case GUC_ACTION_SAVE:
                  stack->state = GUC_SAVE;
                  break;
      }
      stack->source = gconf->source;
      set_stack_value(gconf, &stack->prior);

      gconf->stack = stack;

      /* Ensure we remember to pop at end of xact */
      guc_dirty = true;
}


/*
 * Do GUC processing at main transaction start.
 */
void
AtStart_GUC(void)
{
      /*
       * The nest level should be 0 between transactions; if it isn't, somebody
       * didn't call AtEOXact_GUC, or called it with the wrong nestLevel.  We
       * throw a warning but make no other effort to clean up.
       */
      if (GUCNestLevel != 0)
            elog(WARNING, "GUC nest level = %d at transaction start",
                   GUCNestLevel);
      GUCNestLevel = 1;
}

/*
 * Enter a new nesting level for GUC values.  This is called at subtransaction
 * start and when entering a function that has proconfig settings.      NOTE that
 * we must not risk error here, else subtransaction start will be unhappy.
 */
int
NewGUCNestLevel(void)
{
      return ++GUCNestLevel;
}

/*
 * Do GUC processing at transaction or subtransaction commit or abort, or
 * when exiting a function that has proconfig settings.  (The name is thus
 * a bit of a misnomer; perhaps it should be ExitGUCNestLevel or some such.)
 * During abort, we discard all GUC settings that were applied at nesting
 * levels >= nestLevel.  nestLevel == 1 corresponds to the main transaction.
 */
void
AtEOXact_GUC(bool isCommit, int nestLevel)
{
      bool        still_dirty;
      int               i;

      Assert(nestLevel > 0 && nestLevel <= GUCNestLevel);

      /* Quick exit if nothing's changed in this transaction */
      if (!guc_dirty)
      {
            GUCNestLevel = nestLevel - 1;
            return;
      }

      still_dirty = false;
      for (i = 0; i < num_guc_variables; i++)
      {
            struct config_generic *gconf = guc_variables[i];
            GucStack   *stack;

            /*
             * Process and pop each stack entry within the nest level.  To
             * simplify fmgr_security_definer(), we allow failure exit from a
             * function-with-SET-options to be recovered at the surrounding
             * transaction or subtransaction abort; so there could be more than
             * one stack entry to pop.
             */
            while ((stack = gconf->stack) != NULL &&
                     stack->nest_level >= nestLevel)
            {
                  GucStack   *prev = stack->prev;
                  bool        restorePrior = false;
                  bool        restoreMasked = false;
                  bool        changed;

                  /*
                   * In this next bit, if we don't set either restorePrior or
                   * restoreMasked, we must "discard" any unwanted fields of the
                   * stack entries to avoid leaking memory.  If we do set one of
                   * those flags, unused fields will be cleaned up after restoring.
                   */
                  if (!isCommit)          /* if abort, always restore prior value */
                        restorePrior = true;
                  else if (stack->state == GUC_SAVE)
                        restorePrior = true;
                  else if (stack->nest_level == 1)
                  {
                        /* transaction commit */
                        if (stack->state == GUC_SET_LOCAL)
                              restoreMasked = true;
                        else if (stack->state == GUC_SET)
                        {
                              /* we keep the current active value */
                              discard_stack_value(gconf, &stack->prior);
                        }
                        else  /* must be GUC_LOCAL */
                              restorePrior = true;
                  }
                  else if (prev == NULL ||
                               prev->nest_level < stack->nest_level - 1)
                  {
                        /* decrement entry's level and do not pop it */
                        stack->nest_level--;
                        continue;
                  }
                  else
                  {
                        /*
                         * We have to merge this stack entry into prev. See README for
                         * discussion of this bit.
                         */
                        switch (stack->state)
                        {
                              case GUC_SAVE:
                                    Assert(false);    /* can't get here */

                              case GUC_SET:
                                    /* next level always becomes SET */
                                    discard_stack_value(gconf, &stack->prior);
                                    if (prev->state == GUC_SET_LOCAL)
                                          discard_stack_value(gconf, &prev->masked);
                                    prev->state = GUC_SET;
                                    break;

                              case GUC_LOCAL:
                                    if (prev->state == GUC_SET)
                                    {
                                          /* LOCAL migrates down */
                                          prev->masked = stack->prior;
                                          prev->state = GUC_SET_LOCAL;
                                    }
                                    else
                                    {
                                          /* else just forget this stack level */
                                          discard_stack_value(gconf, &stack->prior);
                                    }
                                    break;

                              case GUC_SET_LOCAL:
                                    /* prior state at this level no longer wanted */
                                    discard_stack_value(gconf, &stack->prior);
                                    /* copy down the masked state */
                                    if (prev->state == GUC_SET_LOCAL)
                                          discard_stack_value(gconf, &prev->masked);
                                    prev->masked = stack->masked;
                                    prev->state = GUC_SET_LOCAL;
                                    break;
                        }
                  }

                  changed = false;

                  if (restorePrior || restoreMasked)
                  {
                        /* Perform appropriate restoration of the stacked value */
                        union config_var_value newvalue;
                        GucSource   newsource;

                        if (restoreMasked)
                        {
                              newvalue = stack->masked;
                              newsource = PGC_S_SESSION;
                        }
                        else
                        {
                              newvalue = stack->prior;
                              newsource = stack->source;
                        }

                        switch (gconf->vartype)
                        {
                              case PGC_BOOL:
                                    {
                                          struct config_bool *conf = (struct config_bool *) gconf;
                                          bool        newval = newvalue.boolval;

                                          if (*conf->variable != newval)
                                          {
                                                if (conf->assign_hook)
                                                      if (!(*conf->assign_hook) (newval,
                                                                                 true, PGC_S_OVERRIDE))
                                                            elog(LOG, "failed to commit %s as %d",
                                                                   conf->gen.name, (int) newval);
                                                *conf->variable = newval;
                                                changed = true;
                                          }
                                          break;
                                    }
                              case PGC_INT:
                                    {
                                          struct config_int *conf = (struct config_int *) gconf;
                                          int               newval = newvalue.intval;

                                          if (*conf->variable != newval)
                                          {
                                                if (conf->assign_hook)
                                                      if (!(*conf->assign_hook) (newval,
                                                                                 true, PGC_S_OVERRIDE))
                                                            elog(LOG, "failed to commit %s as %d",
                                                                   conf->gen.name, newval);
                                                *conf->variable = newval;
                                                changed = true;
                                          }
                                          break;
                                    }
                              case PGC_REAL:
                                    {
                                          struct config_real *conf = (struct config_real *) gconf;
                                          double            newval = newvalue.realval;

                                          if (*conf->variable != newval)
                                          {
                                                if (conf->assign_hook)
                                                      if (!(*conf->assign_hook) (newval,
                                                                                 true, PGC_S_OVERRIDE))
                                                            elog(LOG, "failed to commit %s as %g",
                                                                   conf->gen.name, newval);
                                                *conf->variable = newval;
                                                changed = true;
                                          }
                                          break;
                                    }
                              case PGC_STRING:
                                    {
                                          struct config_string *conf = (struct config_string *) gconf;
                                          char     *newval = newvalue.stringval;

                                          if (*conf->variable != newval)
                                          {
                                                if (conf->assign_hook && newval)
                                                {
                                                      const char *newstr;

                                                      newstr = (*conf->assign_hook) (newval, true,
                                                                                           PGC_S_OVERRIDE);
                                                      if (newstr == NULL)
                                                            elog(LOG, "failed to commit %s as \"%s\"",
                                                                   conf->gen.name, newval);
                                                      else if (newstr != newval)
                                                      {
                                                            /*
                                                             * If newval should now be freed,
                                                             * it'll be taken care of below.
                                                             *
                                                             * See notes in set_config_option
                                                             * about casting
                                                             */
                                                            newval = (char *) newstr;
                                                      }
                                                }

                                                set_string_field(conf, conf->variable, newval);
                                                changed = true;
                                          }

                                          /*
                                           * Release stacked values if not used anymore. We
                                           * could use discard_stack_value() here, but since
                                           * we have type-specific code anyway, might as
                                           * well inline it.
                                           */
                                          set_string_field(conf, &stack->prior.stringval, NULL);
                                          set_string_field(conf, &stack->masked.stringval, NULL);
                                          break;
                                    }
                              case PGC_ENUM:
                                    {
                                          struct config_enum *conf = (struct config_enum *) gconf;
                                          int               newval = newvalue.enumval;

                                          if (*conf->variable != newval)
                                          {
                                                if (conf->assign_hook)
                                                      if (!(*conf->assign_hook) (newval,
                                                                                 true, PGC_S_OVERRIDE))
                                                            elog(LOG, "failed to commit %s as %s",
                                                                   conf->gen.name,
                                                                   config_enum_lookup_by_value(conf, newval));
                                                *conf->variable = newval;
                                                changed = true;
                                          }
                                          break;
                                    }
                        }

                        gconf->source = newsource;
                  }

                  /* Finish popping the state stack */
                  gconf->stack = prev;
                  pfree(stack);

                  /* Report new value if we changed it */
                  if (changed && (gconf->flags & GUC_REPORT))
                        ReportGUCOption(gconf);
            }                                   /* end of stack-popping loop */

            if (stack != NULL)
                  still_dirty = true;
      }

      /* If there are no remaining stack entries, we can reset guc_dirty */
      guc_dirty = still_dirty;

      /* Update nesting level */
      GUCNestLevel = nestLevel - 1;
}


/*
 * Start up automatic reporting of changes to variables marked GUC_REPORT.
 * This is executed at completion of backend startup.
 */
void
BeginReportingGUCOptions(void)
{
      int               i;

      /*
       * Don't do anything unless talking to an interactive frontend of protocol
       * 3.0 or later.
       */
      if (whereToSendOutput != DestRemote ||
            PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
            return;

      reporting_enabled = true;

      /* Transmit initial values of interesting variables */
      for (i = 0; i < num_guc_variables; i++)
      {
            struct config_generic *conf = guc_variables[i];

            if (conf->flags & GUC_REPORT)
                  ReportGUCOption(conf);
      }
}

/*
 * ReportGUCOption: if appropriate, transmit option value to frontend
 */
static void
ReportGUCOption(struct config_generic * record)
{
      if (reporting_enabled && (record->flags & GUC_REPORT))
      {
            char     *val = _ShowOption(record, false);
            StringInfoData msgbuf;

            pq_beginmessage(&msgbuf, 'S');
            pq_sendstring(&msgbuf, record->name);
            pq_sendstring(&msgbuf, val);
            pq_endmessage(&msgbuf);

            pfree(val);
      }
}

/*
 * Try to parse value as an integer.  The accepted formats are the
 * usual decimal, octal, or hexadecimal formats, optionally followed by
 * a unit name if "flags" indicates a unit is allowed.
 *
 * If the string parses okay, return true, else false.
 * If okay and result is not NULL, return the value in *result.
 * If not okay and hintmsg is not NULL, *hintmsg is set to a suitable
 *    HINT message, or NULL if no hint provided.
 */
bool
parse_int(const char *value, int *result, int flags, const char **hintmsg)
{
      int64       val;
      char     *endptr;

      /* To suppress compiler warnings, always set output params */
      if (result)
            *result = 0;
      if (hintmsg)
            *hintmsg = NULL;

      /* We assume here that int64 is at least as wide as long */
      errno = 0;
      val = strtol(value, &endptr, 0);

      if (endptr == value)
            return false;                 /* no HINT for integer syntax error */

      if (errno == ERANGE || val != (int64) ((int32) val))
      {
            if (hintmsg)
                  *hintmsg = gettext_noop("Value exceeds integer range.");
            return false;
      }

      /* allow whitespace between integer and unit */
      while (isspace((unsigned char) *endptr))
            endptr++;

      /* Handle possible unit */
      if (*endptr != '\0')
      {
            /*
             * Note: the multiple-switch coding technique here is a bit tedious,
             * but seems necessary to avoid intermediate-value overflows.
             *
             * If INT64_IS_BUSTED (ie, it's really int32) we will fail to detect
             * overflow due to units conversion, but there are few enough such
             * machines that it does not seem worth trying to be smarter.
             */
            if (flags & GUC_UNIT_MEMORY)
            {
                  /* Set hint for use if no match or trailing garbage */
                  if (hintmsg)
                        *hintmsg = gettext_noop("Valid units for this parameter are \"kB\", \"MB\", and \"GB\".");

#if BLCKSZ < 1024 || BLCKSZ > (1024*1024)
#error BLCKSZ must be between 1KB and 1MB
#endif
#if XLOG_BLCKSZ < 1024 || XLOG_BLCKSZ > (1024*1024)
#error XLOG_BLCKSZ must be between 1KB and 1MB
#endif

                  if (strncmp(endptr, "kB", 2) == 0)
                  {
                        endptr += 2;
                        switch (flags & GUC_UNIT_MEMORY)
                        {
                              case GUC_UNIT_BLOCKS:
                                    val /= (BLCKSZ / 1024);
                                    break;
                              case GUC_UNIT_XBLOCKS:
                                    val /= (XLOG_BLCKSZ / 1024);
                                    break;
                        }
                  }
                  else if (strncmp(endptr, "MB", 2) == 0)
                  {
                        endptr += 2;
                        switch (flags & GUC_UNIT_MEMORY)
                        {
                              case GUC_UNIT_KB:
                                    val *= KB_PER_MB;
                                    break;
                              case GUC_UNIT_BLOCKS:
                                    val *= KB_PER_MB / (BLCKSZ / 1024);
                                    break;
                              case GUC_UNIT_XBLOCKS:
                                    val *= KB_PER_MB / (XLOG_BLCKSZ / 1024);
                                    break;
                        }
                  }
                  else if (strncmp(endptr, "GB", 2) == 0)
                  {
                        endptr += 2;
                        switch (flags & GUC_UNIT_MEMORY)
                        {
                              case GUC_UNIT_KB:
                                    val *= KB_PER_GB;
                                    break;
                              case GUC_UNIT_BLOCKS:
                                    val *= KB_PER_GB / (BLCKSZ / 1024);
                                    break;
                              case GUC_UNIT_XBLOCKS:
                                    val *= KB_PER_GB / (XLOG_BLCKSZ / 1024);
                                    break;
                        }
                  }
            }
            else if (flags & GUC_UNIT_TIME)
            {
                  /* Set hint for use if no match or trailing garbage */
                  if (hintmsg)
                        *hintmsg = gettext_noop("Valid units for this parameter are \"ms\", \"s\", \"min\", \"h\", and \"d\".");

                  if (strncmp(endptr, "ms", 2) == 0)
                  {
                        endptr += 2;
                        switch (flags & GUC_UNIT_TIME)
                        {
                              case GUC_UNIT_S:
                                    val /= MS_PER_S;
                                    break;
                              case GUC_UNIT_MIN:
                                    val /= MS_PER_MIN;
                                    break;
                        }
                  }
                  else if (strncmp(endptr, "s", 1) == 0)
                  {
                        endptr += 1;
                        switch (flags & GUC_UNIT_TIME)
                        {
                              case GUC_UNIT_MS:
                                    val *= MS_PER_S;
                                    break;
                              case GUC_UNIT_MIN:
                                    val /= S_PER_MIN;
                                    break;
                        }
                  }
                  else if (strncmp(endptr, "min", 3) == 0)
                  {
                        endptr += 3;
                        switch (flags & GUC_UNIT_TIME)
                        {
                              case GUC_UNIT_MS:
                                    val *= MS_PER_MIN;
                                    break;
                              case GUC_UNIT_S:
                                    val *= S_PER_MIN;
                                    break;
                        }
                  }
                  else if (strncmp(endptr, "h", 1) == 0)
                  {
                        endptr += 1;
                        switch (flags & GUC_UNIT_TIME)
                        {
                              case GUC_UNIT_MS:
                                    val *= MS_PER_H;
                                    break;
                              case GUC_UNIT_S:
                                    val *= S_PER_H;
                                    break;
                              case GUC_UNIT_MIN:
                                    val *= MIN_PER_H;
                                    break;
                        }
                  }
                  else if (strncmp(endptr, "d", 1) == 0)
                  {
                        endptr += 1;
                        switch (flags & GUC_UNIT_TIME)
                        {
                              case GUC_UNIT_MS:
                                    val *= MS_PER_D;
                                    break;
                              case GUC_UNIT_S:
                                    val *= S_PER_D;
                                    break;
                              case GUC_UNIT_MIN:
                                    val *= MIN_PER_D;
                                    break;
                        }
                  }
            }

            /* allow whitespace after unit */
            while (isspace((unsigned char) *endptr))
                  endptr++;

            if (*endptr != '\0')
                  return false;           /* appropriate hint, if any, already set */

            /* Check for overflow due to units conversion */
            if (val != (int64) ((int32) val))
            {
                  if (hintmsg)
                        *hintmsg = gettext_noop("Value exceeds integer range.");
                  return false;
            }
      }

      if (result)
            *result = (int) val;
      return true;
}



/*
 * Try to parse value as a floating point number in the usual format.
 * If the string parses okay, return true, else false.
 * If okay and result is not NULL, return the value in *result.
 */
bool
parse_real(const char *value, double *result)
{
      double            val;
      char     *endptr;

      if (result)
            *result = 0;                  /* suppress compiler warning */

      errno = 0;
      val = strtod(value, &endptr);
      if (endptr == value || errno == ERANGE)
            return false;

      /* allow whitespace after number */
      while (isspace((unsigned char) *endptr))
            endptr++;
      if (*endptr != '\0')
            return false;

      if (result)
            *result = val;
      return true;
}


/*
 * Lookup the name for an enum option with the selected value.
 * Should only ever be called with known-valid values, so throws
 * an elog(ERROR) if the enum option is not found.
 *
 * The returned string is a pointer to static data and not
 * allocated for modification.
 */
const char *
config_enum_lookup_by_value(struct config_enum * record, int val)
{
      const struct config_enum_entry *entry;

      for (entry = record->options; entry && entry->name; entry++)
      {
            if (entry->val == val)
                  return entry->name;
      }

      elog(ERROR, "could not find enum option %d for %s",
             val, record->gen.name);
      return NULL;                        /* silence compiler */
}


/*
 * Lookup the value for an enum option with the selected name
 * (case-insensitive).
 * If the enum option is found, sets the retval value and returns
 * true. If it's not found, return FALSE and retval is set to 0.
 */
bool
config_enum_lookup_by_name(struct config_enum * record, const char *value,
                                       int *retval)
{
      const struct config_enum_entry *entry;

      for (entry = record->options; entry && entry->name; entry++)
      {
            if (pg_strcasecmp(value, entry->name) == 0)
            {
                  *retval = entry->val;
                  return TRUE;
            }
      }

      *retval = 0;
      return FALSE;
}


/*
 * Return a list of all available options for an enum, excluding
 * hidden ones, separated by the given separator.
 * If prefix is non-NULL, it is added before the first enum value.
 * If suffix is non-NULL, it is added to the end of the string.
 */
static char *
config_enum_get_options(struct config_enum * record, const char *prefix,
                                    const char *suffix, const char *separator)
{
      const struct config_enum_entry *entry;
      StringInfoData retstr;
      int               seplen;

      initStringInfo(&retstr);
      appendStringInfoString(&retstr, prefix);

      seplen = strlen(separator);
      for (entry = record->options; entry && entry->name; entry++)
      {
            if (!entry->hidden)
            {
                  appendStringInfoString(&retstr, entry->name);
                  appendBinaryStringInfo(&retstr, separator, seplen);
            }
      }

      /*
       * All the entries may have been hidden, leaving the string empty if no
       * prefix was given. This indicates a broken GUC setup, since there is no
       * use for an enum without any values, so we just check to make sure we
       * don't write to invalid memory instead of actually trying to do
       * something smart with it.
       */
      if (retstr.len >= seplen)
      {
            /* Replace final separator */
            retstr.data[retstr.len - seplen] = '\0';
            retstr.len -= seplen;
      }

      appendStringInfoString(&retstr, suffix);

      return retstr.data;
}

/*
 * Call a GucStringAssignHook function, being careful to free the
 * "newval" string if the hook ereports.
 *
 * This is split out of set_config_option just to avoid the "volatile"
 * qualifiers that would otherwise have to be plastered all over.
 */
static const char *
call_string_assign_hook(GucStringAssignHook assign_hook,
                                    char *newval, bool doit, GucSource source)
{
      const char *result;

      PG_TRY();
      {
            result = (*assign_hook) (newval, doit, source);
      }
      PG_CATCH();
      {
            free(newval);
            PG_RE_THROW();
      }
      PG_END_TRY();

      return result;
}


/*
 * Sets option `name' to given value. The value should be a string
 * which is going to be parsed and converted to the appropriate data
 * type.  The context and source parameters indicate in which context this
 * function is being called so it can apply the access restrictions
 * properly.
 *
 * If value is NULL, set the option to its default value (normally the
 * reset_val, but if source == PGC_S_DEFAULT we instead use the boot_val).
 *
 * action indicates whether to set the value globally in the session, locally
 * to the current top transaction, or just for the duration of a function call.
 *
 * If changeVal is false then don't really set the option but do all
 * the checks to see if it would work.
 *
 * If there is an error (non-existing option, invalid value) then an
 * ereport(ERROR) is thrown *unless* this is called in a context where we
 * don't want to ereport (currently, startup or SIGHUP config file reread).
 * In that case we write a suitable error message via ereport(LOG) and
 * return false. This is working around the deficiencies in the ereport
 * mechanism, so don't blame me.  In all other cases, the function
 * returns true, including cases where the input is valid but we chose
 * not to apply it because of context or source-priority considerations.
 *
 * See also SetConfigOption for an external interface.
 */
bool
set_config_option(const char *name, const char *value,
                          GucContext context, GucSource source,
                          GucAction action, bool changeVal)
{
      struct config_generic *record;
      int               elevel;
      bool        makeDefault;

      if (context == PGC_SIGHUP || source == PGC_S_DEFAULT)
      {
            /*
             * To avoid cluttering the log, only the postmaster bleats loudly
             * about problems with the config file.
             */
            elevel = IsUnderPostmaster ? DEBUG3 : LOG;
      }
      else if (source == PGC_S_DATABASE || source == PGC_S_USER)
            elevel = WARNING;
      else
            elevel = ERROR;

      record = find_option(name, true, elevel);
      if (record == NULL)
      {
            ereport(elevel,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("unrecognized configuration parameter \"%s\"", name)));
            return false;
      }

      /*
       * If source is postgresql.conf, mark the found record with
       * GUC_IS_IN_FILE. This is for the convenience of ProcessConfigFile.  Note
       * that we do it even if changeVal is false, since ProcessConfigFile wants
       * the marking to occur during its testing pass.
       */
      if (source == PGC_S_FILE)
            record->status |= GUC_IS_IN_FILE;

      /*
       * Check if the option can be set at this time. See guc.h for the precise
       * rules. Note that we don't want to throw errors if we're in the SIGHUP
       * context. In that case we just ignore the attempt and return true.
       */
      switch (record->context)
      {
            case PGC_INTERNAL:
                  if (context == PGC_SIGHUP)
                        return true;
                  if (context != PGC_INTERNAL)
                  {
                        ereport(elevel,
                                    (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                     errmsg("parameter \"%s\" cannot be changed",
                                                name)));
                        return false;
                  }
                  break;
            case PGC_POSTMASTER:
                  if (context == PGC_SIGHUP)
                  {
                        /*
                         * We are reading a PGC_POSTMASTER var from postgresql.conf.
                         * We can't change the setting, so give a warning if the DBA
                         * tries to change it.  (Throwing an error would be more
                         * consistent, but seems overly rigid.)
                         */
                        if (changeVal && !is_newvalue_equal(record, value))
                              ereport(elevel,
                                          (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                 errmsg("attempted change of parameter \"%s\" ignored",
                                            name),
                                           errdetail("This parameter cannot be changed after server start.")));
                        return true;
                  }
                  if (context != PGC_POSTMASTER)
                  {
                        ereport(elevel,
                                    (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                 errmsg("attempted change of parameter \"%s\" ignored",
                                            name),
                                     errdetail("This parameter cannot be changed after server start.")));
                        return false;
                  }
                  break;
            case PGC_SIGHUP:
                  if (context != PGC_SIGHUP && context != PGC_POSTMASTER)
                  {
                        ereport(elevel,
                                    (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                     errmsg("parameter \"%s\" cannot be changed now",
                                                name)));
                        return false;
                  }

                  /*
                   * Hmm, the idea of the SIGHUP context is "ought to be global, but
                   * can be changed after postmaster start". But there's nothing
                   * that prevents a crafty administrator from sending SIGHUP
                   * signals to individual backends only.
                   */
                  break;
            case PGC_BACKEND:
                  if (context == PGC_SIGHUP)
                  {
                        /*
                         * If a PGC_BACKEND parameter is changed in the config file,
                         * we want to accept the new value in the postmaster (whence
                         * it will propagate to subsequently-started backends), but
                         * ignore it in existing backends.  This is a tad klugy, but
                         * necessary because we don't re-read the config file during
                         * backend start.
                         */
                        if (IsUnderPostmaster)
                              return true;
                  }
                  else if (context != PGC_BACKEND && context != PGC_POSTMASTER)
                  {
                        ereport(elevel,
                                    (errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
                                     errmsg("parameter \"%s\" cannot be set after connection start",
                                                name)));
                        return false;
                  }
                  break;
            case PGC_SUSET:
                  if (context == PGC_USERSET || context == PGC_BACKEND)
                  {
                        ereport(elevel,
                                    (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                                     errmsg("permission denied to set parameter \"%s\"",
                                                name)));
                        return false;
                  }
                  break;
            case PGC_USERSET:
                  /* always okay */
                  break;
      }

      /*
       * Should we set reset/stacked values?    (If so, the behavior is not
       * transactional.)      This is done either when we get a default value from
       * the database's/user's/client's default settings or when we reset a
       * value to its default.
       */
      makeDefault = changeVal && (source <= PGC_S_OVERRIDE) &&
            ((value != NULL) || source == PGC_S_DEFAULT);

      /*
       * Ignore attempted set if overridden by previously processed setting.
       * However, if changeVal is false then plow ahead anyway since we are
       * trying to find out if the value is potentially good, not actually use
       * it. Also keep going if makeDefault is true, since we may want to set
       * the reset/stacked values even if we can't set the variable itself.
       */
      if (record->source > source)
      {
            if (changeVal && !makeDefault)
            {
                  elog(DEBUG3, "\"%s\": setting ignored because previous source is higher priority",
                         name);
                  return true;
            }
            changeVal = false;
      }

      /*
       * Evaluate value and set variable.
       */
      switch (record->vartype)
      {
            case PGC_BOOL:
                  {
                        struct config_bool *conf = (struct config_bool *) record;
                        bool        newval;

                        if (value)
                        {
                              if (!parse_bool(value, &newval))
                              {
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                      errmsg("parameter \"%s\" requires a Boolean value",
                                                 name)));
                                    return false;
                              }
                        }
                        else if (source == PGC_S_DEFAULT)
                              newval = conf->boot_val;
                        else
                        {
                              newval = conf->reset_val;
                              source = conf->gen.reset_source;
                        }

                        /* Save old value to support transaction abort */
                        if (changeVal && !makeDefault)
                              push_old_value(&conf->gen, action);

                        if (conf->assign_hook)
                              if (!(*conf->assign_hook) (newval, changeVal, source))
                              {
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                           errmsg("invalid value for parameter \"%s\": %d",
                                                      name, (int) newval)));
                                    return false;
                              }

                        if (changeVal)
                        {
                              *conf->variable = newval;
                              conf->gen.source = source;
                        }
                        if (makeDefault)
                        {
                              GucStack   *stack;

                              if (conf->gen.reset_source <= source)
                              {
                                    conf->reset_val = newval;
                                    conf->gen.reset_source = source;
                              }
                              for (stack = conf->gen.stack; stack; stack = stack->prev)
                              {
                                    if (stack->source <= source)
                                    {
                                          stack->prior.boolval = newval;
                                          stack->source = source;
                                    }
                              }
                        }
                        break;
                  }

            case PGC_INT:
                  {
                        struct config_int *conf = (struct config_int *) record;
                        int               newval;

                        if (value)
                        {
                              const char *hintmsg;

                              if (!parse_int(value, &newval, conf->gen.flags, &hintmsg))
                              {
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                     errmsg("invalid value for parameter \"%s\": \"%s\"",
                                                name, value),
                                                 hintmsg ? errhint("%s", _(hintmsg)) : 0));
                                    return false;
                              }
                              if (newval < conf->min || newval > conf->max)
                              {
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
                                                            newval, name, conf->min, conf->max)));
                                    return false;
                              }
                        }
                        else if (source == PGC_S_DEFAULT)
                              newval = conf->boot_val;
                        else
                        {
                              newval = conf->reset_val;
                              source = conf->gen.reset_source;
                        }

                        /* Save old value to support transaction abort */
                        if (changeVal && !makeDefault)
                              push_old_value(&conf->gen, action);

                        if (conf->assign_hook)
                              if (!(*conf->assign_hook) (newval, changeVal, source))
                              {
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                           errmsg("invalid value for parameter \"%s\": %d",
                                                      name, newval)));
                                    return false;
                              }

                        if (changeVal)
                        {
                              *conf->variable = newval;
                              conf->gen.source = source;
                        }
                        if (makeDefault)
                        {
                              GucStack   *stack;

                              if (conf->gen.reset_source <= source)
                              {
                                    conf->reset_val = newval;
                                    conf->gen.reset_source = source;
                              }
                              for (stack = conf->gen.stack; stack; stack = stack->prev)
                              {
                                    if (stack->source <= source)
                                    {
                                          stack->prior.intval = newval;
                                          stack->source = source;
                                    }
                              }
                        }
                        break;
                  }

            case PGC_REAL:
                  {
                        struct config_real *conf = (struct config_real *) record;
                        double            newval;

                        if (value)
                        {
                              if (!parse_real(value, &newval))
                              {
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                      errmsg("parameter \"%s\" requires a numeric value",
                                                 name)));
                                    return false;
                              }
                              if (newval < conf->min || newval > conf->max)
                              {
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                                 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
                                                            newval, name, conf->min, conf->max)));
                                    return false;
                              }
                        }
                        else if (source == PGC_S_DEFAULT)
                              newval = conf->boot_val;
                        else
                        {
                              newval = conf->reset_val;
                              source = conf->gen.reset_source;
                        }

                        /* Save old value to support transaction abort */
                        if (changeVal && !makeDefault)
                              push_old_value(&conf->gen, action);

                        if (conf->assign_hook)
                              if (!(*conf->assign_hook) (newval, changeVal, source))
                              {
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                           errmsg("invalid value for parameter \"%s\": %g",
                                                      name, newval)));
                                    return false;
                              }

                        if (changeVal)
                        {
                              *conf->variable = newval;
                              conf->gen.source = source;
                        }
                        if (makeDefault)
                        {
                              GucStack   *stack;

                              if (conf->gen.reset_source <= source)
                              {
                                    conf->reset_val = newval;
                                    conf->gen.reset_source = source;
                              }
                              for (stack = conf->gen.stack; stack; stack = stack->prev)
                              {
                                    if (stack->source <= source)
                                    {
                                          stack->prior.realval = newval;
                                          stack->source = source;
                                    }
                              }
                        }
                        break;
                  }

            case PGC_STRING:
                  {
                        struct config_string *conf = (struct config_string *) record;
                        char     *newval;

                        if (value)
                        {
                              newval = guc_strdup(elevel, value);
                              if (newval == NULL)
                                    return false;

                              /*
                               * The only sort of "parsing" check we need to do is apply
                               * truncation if GUC_IS_NAME.
                               */
                              if (conf->gen.flags & GUC_IS_NAME)
                                    truncate_identifier(newval, strlen(newval), true);
                        }
                        else if (source == PGC_S_DEFAULT)
                        {
                              if (conf->boot_val == NULL)
                                    newval = NULL;
                              else
                              {
                                    newval = guc_strdup(elevel, conf->boot_val);
                                    if (newval == NULL)
                                          return false;
                              }
                        }
                        else
                        {
                              /*
                               * We could possibly avoid strdup here, but easier to make
                               * this case work the same as the normal assignment case;
                               * note the possible free of newval below.
                               */
                              if (conf->reset_val == NULL)
                                    newval = NULL;
                              else
                              {
                                    newval = guc_strdup(elevel, conf->reset_val);
                                    if (newval == NULL)
                                          return false;
                              }
                              source = conf->gen.reset_source;
                        }

                        /* Save old value to support transaction abort */
                        if (changeVal && !makeDefault)
                              push_old_value(&conf->gen, action);

                        if (conf->assign_hook && newval)
                        {
                              const char *hookresult;

                              /*
                               * If the hook ereports, we have to make sure we free
                               * newval, else it will be a permanent memory leak.
                               */
                              hookresult = call_string_assign_hook(conf->assign_hook,
                                                                                     newval,
                                                                                     changeVal,
                                                                                     source);
                              if (hookresult == NULL)
                              {
                                    free(newval);
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                     errmsg("invalid value for parameter \"%s\": \"%s\"",
                                                name, value ? value : "")));
                                    return false;
                              }
                              else if (hookresult != newval)
                              {
                                    free(newval);

                                    /*
                                     * Having to cast away const here is annoying, but the
                                     * alternative is to declare assign_hooks as returning
                                     * char*, which would mean they'd have to cast away
                                     * const, or as both taking and returning char*, which
                                     * doesn't seem attractive either --- we don't want
                                     * them to scribble on the passed str.
                                     */
                                    newval = (char *) hookresult;
                              }
                        }

                        if (changeVal)
                        {
                              set_string_field(conf, conf->variable, newval);
                              conf->gen.source = source;
                        }
                        if (makeDefault)
                        {
                              GucStack   *stack;

                              if (conf->gen.reset_source <= source)
                              {
                                    set_string_field(conf, &conf->reset_val, newval);
                                    conf->gen.reset_source = source;
                              }
                              for (stack = conf->gen.stack; stack; stack = stack->prev)
                              {
                                    if (stack->source <= source)
                                    {
                                          set_string_field(conf, &stack->prior.stringval,
                                                                   newval);
                                          stack->source = source;
                                    }
                              }
                        }
                        /* Perhaps we didn't install newval anywhere */
                        if (newval && !string_field_used(conf, newval))
                              free(newval);
                        break;
                  }
            case PGC_ENUM:
                  {
                        struct config_enum *conf = (struct config_enum *) record;
                        int               newval;

                        if (value)
                        {
                              if (!config_enum_lookup_by_name(conf, value, &newval))
                              {
                                    char     *hintmsg;

                                    hintmsg = config_enum_get_options(conf,
                                                                                    "Available values: ",
                                                                                      ".", ", ");

                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                     errmsg("invalid value for parameter \"%s\": \"%s\"",
                                                name, value),
                                                 hintmsg ? errhint("%s", _(hintmsg)) : 0));

                                    if (hintmsg)
                                          pfree(hintmsg);
                                    return false;
                              }
                        }
                        else if (source == PGC_S_DEFAULT)
                              newval = conf->boot_val;
                        else
                        {
                              newval = conf->reset_val;
                              source = conf->gen.reset_source;
                        }

                        /* Save old value to support transaction abort */
                        if (changeVal && !makeDefault)
                              push_old_value(&conf->gen, action);

                        if (conf->assign_hook)
                              if (!(*conf->assign_hook) (newval, changeVal, source))
                              {
                                    ereport(elevel,
                                                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                     errmsg("invalid value for parameter \"%s\": \"%s\"",
                                                name,
                                                config_enum_lookup_by_value(conf, newval))));
                                    return false;
                              }

                        if (changeVal)
                        {
                              *conf->variable = newval;
                              conf->gen.source = source;
                        }
                        if (makeDefault)
                        {
                              GucStack   *stack;

                              if (conf->gen.reset_source <= source)
                              {
                                    conf->reset_val = newval;
                                    conf->gen.reset_source = source;
                              }
                              for (stack = conf->gen.stack; stack; stack = stack->prev)
                              {
                                    if (stack->source <= source)
                                    {
                                          stack->prior.enumval = newval;
                                          stack->source = source;
                                    }
                              }
                        }
                        break;
                  }
      }

      if (changeVal && (record->flags & GUC_REPORT))
            ReportGUCOption(record);

      return true;
}


/*
 * Set the fields for source file and line number the setting came from.
 */
static void
set_config_sourcefile(const char *name, char *sourcefile, int sourceline)
{
      struct config_generic *record;
      int               elevel;

      /*
       * To avoid cluttering the log, only the postmaster bleats loudly about
       * problems with the config file.
       */
      elevel = IsUnderPostmaster ? DEBUG3 : LOG;

      record = find_option(name, true, elevel);
      /* should not happen */
      if (record == NULL)
            elog(ERROR, "unrecognized configuration parameter \"%s\"", name);

      sourcefile = guc_strdup(elevel, sourcefile);
      if (record->sourcefile)
            free(record->sourcefile);
      record->sourcefile = sourcefile;
      record->sourceline = sourceline;
}

/*
 * Set a config option to the given value. See also set_config_option,
 * this is just the wrapper to be called from outside GUC.  NB: this
 * is used only for non-transactional operations.
 *
 * Note: there is no support here for setting source file/line, as it
 * is currently not needed.
 */
void
SetConfigOption(const char *name, const char *value,
                        GucContext context, GucSource source)
{
      (void) set_config_option(name, value, context, source,
                                           GUC_ACTION_SET, true);
}



/*
 * Fetch the current value of the option `name'. If the option doesn't exist,
 * throw an ereport and don't return.
 *
 * The string is *not* allocated for modification and is really only
 * valid until the next call to configuration related functions.
 */
const char *
GetConfigOption(const char *name)
{
      struct config_generic *record;
      static char buffer[256];

      record = find_option(name, false, ERROR);
      if (record == NULL)
            ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("unrecognized configuration parameter \"%s\"", name)));
      if ((record->flags & GUC_SUPERUSER_ONLY) && !superuser())
            ereport(ERROR,
                        (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                         errmsg("must be superuser to examine \"%s\"", name)));

      switch (record->vartype)
      {
            case PGC_BOOL:
                  return *((struct config_bool *) record)->variable ? "on" : "off";

            case PGC_INT:
                  snprintf(buffer, sizeof(buffer), "%d",
                               *((struct config_int *) record)->variable);
                  return buffer;

            case PGC_REAL:
                  snprintf(buffer, sizeof(buffer), "%g",
                               *((struct config_real *) record)->variable);
                  return buffer;

            case PGC_STRING:
                  return *((struct config_string *) record)->variable;

            case PGC_ENUM:
                  return config_enum_lookup_by_value((struct config_enum *) record,
                                                 *((struct config_enum *) record)->variable);
      }
      return NULL;
}

/*
 * Get the RESET value associated with the given option.
 *
 * Note: this is not re-entrant, due to use of static result buffer;
 * not to mention that a string variable could have its reset_val changed.
 * Beware of assuming the result value is good for very long.
 */
const char *
GetConfigOptionResetString(const char *name)
{
      struct config_generic *record;
      static char buffer[256];

      record = find_option(name, false, ERROR);
      if (record == NULL)
            ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("unrecognized configuration parameter \"%s\"", name)));
      if ((record->flags & GUC_SUPERUSER_ONLY) && !superuser())
            ereport(ERROR,
                        (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                         errmsg("must be superuser to examine \"%s\"", name)));

      switch (record->vartype)
      {
            case PGC_BOOL:
                  return ((struct config_bool *) record)->reset_val ? "on" : "off";

            case PGC_INT:
                  snprintf(buffer, sizeof(buffer), "%d",
                               ((struct config_int *) record)->reset_val);
                  return buffer;

            case PGC_REAL:
                  snprintf(buffer, sizeof(buffer), "%g",
                               ((struct config_real *) record)->reset_val);
                  return buffer;

            case PGC_STRING:
                  return ((struct config_string *) record)->reset_val;

            case PGC_ENUM:
                  return config_enum_lookup_by_value((struct config_enum *) record,
                                                 ((struct config_enum *) record)->reset_val);
      }
      return NULL;
}

/*
 * Detect whether the given configuration option can only be set by
 * a superuser.
 */
bool
IsSuperuserConfigOption(const char *name)
{
      struct config_generic *record;

      record = find_option(name, false, ERROR);
      /* On an unrecognized name, don't error, just return false. */
      if (record == NULL)
            return false;
      return (record->context == PGC_SUSET);
}


/*
 * GUC_complaint_elevel
 *          Get the ereport error level to use in an assign_hook's error report.
 *
 * This should be used by assign hooks that want to emit a custom error
 * report (in addition to the generic "invalid value for option FOO" that
 * guc.c will provide).  Note that the result might be ERROR or a lower
 * level, so the caller must be prepared for control to return from ereport,
 * or not.  If control does return, return false/NULL from the hook function.
 *
 * At some point it'd be nice to replace this with a mechanism that allows
 * the custom message to become the DETAIL line of guc.c's generic message.
 */
int
GUC_complaint_elevel(GucSource source)
{
      int               elevel;

      if (source == PGC_S_FILE)
      {
            /*
             * To avoid cluttering the log, only the postmaster bleats loudly
             * about problems with the config file.
             */
            elevel = IsUnderPostmaster ? DEBUG3 : LOG;
      }
      else if (source == PGC_S_OVERRIDE)
      {
            /*
             * If we're a postmaster child, this is probably "undo" during
             * transaction abort, so we don't want to clutter the log.  There's a
             * small chance of a real problem with an OVERRIDE setting, though, so
             * suppressing the message entirely wouldn't be desirable.
             */
            elevel = IsUnderPostmaster ? DEBUG5 : LOG;
      }
      else if (source < PGC_S_INTERACTIVE)
            elevel = LOG;
      else
            elevel = ERROR;

      return elevel;
}


/*
 * flatten_set_variable_args
 *          Given a parsenode List as emitted by the grammar for SET,
 *          convert to the flat string representation used by GUC.
 *
 * We need to be told the name of the variable the args are for, because
 * the flattening rules vary (ugh).
 *
 * The result is NULL if args is NIL (ie, SET ... TO DEFAULT), otherwise
 * a palloc'd string.
 */
static char *
flatten_set_variable_args(const char *name, List *args)
{
      struct config_generic *record;
      int               flags;
      StringInfoData buf;
      ListCell   *l;

      /* Fast path if just DEFAULT */
      if (args == NIL)
            return NULL;

      /* Else get flags for the variable */
      record = find_option(name, true, ERROR);
      if (record == NULL)
            ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("unrecognized configuration parameter \"%s\"", name)));

      flags = record->flags;

      /* Complain if list input and non-list variable */
      if ((flags & GUC_LIST_INPUT) == 0 &&
            list_length(args) != 1)
            ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("SET %s takes only one argument", name)));

      initStringInfo(&buf);

      /*
       * Each list member may be a plain A_Const node, or an A_Const within a
       * TypeCast; the latter case is supported only for ConstInterval arguments
       * (for SET TIME ZONE).
       */
      foreach(l, args)
      {
            Node     *arg = (Node *) lfirst(l);
            char     *val;
            TypeName   *typename = NULL;
            A_Const    *con;

            if (l != list_head(args))
                  appendStringInfo(&buf, ", ");

            if (IsA(arg, TypeCast))
            {
                  TypeCast   *tc = (TypeCast *) arg;

                  arg = tc->arg;
                  typename = tc->typename;
            }

            if (!IsA(arg, A_Const))
                  elog(ERROR, "unrecognized node type: %d", (int) nodeTag(arg));
            con = (A_Const *) arg;

            switch (nodeTag(&con->val))
            {
                  case T_Integer:
                        appendStringInfo(&buf, "%ld", intVal(&con->val));
                        break;
                  case T_Float:
                        /* represented as a string, so just copy it */
                        appendStringInfoString(&buf, strVal(&con->val));
                        break;
                  case T_String:
                        val = strVal(&con->val);
                        if (typename != NULL)
                        {
                              /*
                               * Must be a ConstInterval argument for TIME ZONE. Coerce
                               * to interval and back to normalize the value and account
                               * for any typmod.
                               */
                              Oid               typoid;
                              int32       typmod;
                              Datum       interval;
                              char     *intervalout;

                              typoid = typenameTypeId(NULL, typename, &typmod);
                              Assert(typoid == INTERVALOID);

                              interval =
                                    DirectFunctionCall3(interval_in,
                                                                  CStringGetDatum(val),
                                                                  ObjectIdGetDatum(InvalidOid),
                                                                  Int32GetDatum(typmod));

                              intervalout =
                                    DatumGetCString(DirectFunctionCall1(interval_out,
                                                                                          interval));
                              appendStringInfo(&buf, "INTERVAL '%s'", intervalout);
                        }
                        else
                        {
                              /*
                               * Plain string literal or identifier.    For quote mode,
                               * quote it if it's not a vanilla identifier.
                               */
                              if (flags & GUC_LIST_QUOTE)
                                    appendStringInfoString(&buf, quote_identifier(val));
                              else
                                    appendStringInfoString(&buf, val);
                        }
                        break;
                  default:
                        elog(ERROR, "unrecognized node type: %d",
                               (int) nodeTag(&con->val));
                        break;
            }
      }

      return buf.data;
}


/*
 * SET command
 */
void
ExecSetVariableStmt(VariableSetStmt *stmt)
{
      GucAction   action = stmt->is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET;

      switch (stmt->kind)
      {
            case VAR_SET_VALUE:
            case VAR_SET_CURRENT:
                  set_config_option(stmt->name,
                                            ExtractSetVariableArgs(stmt),
                                            (superuser() ? PGC_SUSET : PGC_USERSET),
                                            PGC_S_SESSION,
                                            action,
                                            true);
                  break;
            case VAR_SET_MULTI:

                  /*
                   * Special case for special SQL syntax that effectively sets more
                   * than one variable per statement.
                   */
                  if (strcmp(stmt->name, "TRANSACTION") == 0)
                  {
                        ListCell   *head;

                        foreach(head, stmt->args)
                        {
                              DefElem    *item = (DefElem *) lfirst(head);

                              if (strcmp(item->defname, "transaction_isolation") == 0)
                                    SetPGVariable("transaction_isolation",
                                                        list_make1(item->arg), stmt->is_local);
                              else if (strcmp(item->defname, "transaction_read_only") == 0)
                                    SetPGVariable("transaction_read_only",
                                                        list_make1(item->arg), stmt->is_local);
                              else
                                    elog(ERROR, "unexpected SET TRANSACTION element: %s",
                                           item->defname);
                        }
                  }
                  else if (strcmp(stmt->name, "SESSION CHARACTERISTICS") == 0)
                  {
                        ListCell   *head;

                        foreach(head, stmt->args)
                        {
                              DefElem    *item = (DefElem *) lfirst(head);

                              if (strcmp(item->defname, "transaction_isolation") == 0)
                                    SetPGVariable("default_transaction_isolation",
                                                        list_make1(item->arg), stmt->is_local);
                              else if (strcmp(item->defname, "transaction_read_only") == 0)
                                    SetPGVariable("default_transaction_read_only",
                                                        list_make1(item->arg), stmt->is_local);
                              else
                                    elog(ERROR, "unexpected SET SESSION element: %s",
                                           item->defname);
                        }
                  }
                  else
                        elog(ERROR, "unexpected SET MULTI element: %s",
                               stmt->name);
                  break;
            case VAR_SET_DEFAULT:
            case VAR_RESET:
                  set_config_option(stmt->name,
                                            NULL,
                                            (superuser() ? PGC_SUSET : PGC_USERSET),
                                            PGC_S_SESSION,
                                            action,
                                            true);
                  break;
            case VAR_RESET_ALL:
                  ResetAllOptions();
                  break;
      }
}

/*
 * Get the value to assign for a VariableSetStmt, or NULL if it's RESET.
 * The result is palloc'd.
 *
 * This is exported for use by actions such as ALTER ROLE SET.
 */
char *
ExtractSetVariableArgs(VariableSetStmt *stmt)
{
      switch (stmt->kind)
      {
            case VAR_SET_VALUE:
                  return flatten_set_variable_args(stmt->name, stmt->args);
            case VAR_SET_CURRENT:
                  return GetConfigOptionByName(stmt->name, NULL);
            default:
                  return NULL;
      }
}

/*
 * SetPGVariable - SET command exported as an easily-C-callable function.
 *
 * This provides access to SET TO value, as well as SET TO DEFAULT (expressed
 * by passing args == NIL), but not SET FROM CURRENT functionality.
 */
void
SetPGVariable(const char *name, List *args, bool is_local)
{
      char     *argstring = flatten_set_variable_args(name, args);

      /* Note SET DEFAULT (argstring == NULL) is equivalent to RESET */
      set_config_option(name,
                                argstring,
                                (superuser() ? PGC_SUSET : PGC_USERSET),
                                PGC_S_SESSION,
                                is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET,
                                true);
}

/*
 * SET command wrapped as a SQL callable function.
 */
Datum
set_config_by_name(PG_FUNCTION_ARGS)
{
      char     *name;
      char     *value;
      char     *new_value;
      bool        is_local;

      if (PG_ARGISNULL(0))
            ereport(ERROR,
                        (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
                         errmsg("SET requires parameter name")));

      /* Get the GUC variable name */
      name = TextDatumGetCString(PG_GETARG_DATUM(0));

      /* Get the desired value or set to NULL for a reset request */
      if (PG_ARGISNULL(1))
            value = NULL;
      else
            value = TextDatumGetCString(PG_GETARG_DATUM(1));

      /*
       * Get the desired state of is_local. Default to false if provided value
       * is NULL
       */
      if (PG_ARGISNULL(2))
            is_local = false;
      else
            is_local = PG_GETARG_BOOL(2);

      /* Note SET DEFAULT (argstring == NULL) is equivalent to RESET */
      set_config_option(name,
                                value,
                                (superuser() ? PGC_SUSET : PGC_USERSET),
                                PGC_S_SESSION,
                                is_local ? GUC_ACTION_LOCAL : GUC_ACTION_SET,
                                true);

      /* get the new current value */
      new_value = GetConfigOptionByName(name, NULL);

      /* Convert return string to text */
      PG_RETURN_TEXT_P(cstring_to_text(new_value));
}


/*
 * Common code for DefineCustomXXXVariable subroutines: allocate the
 * new variable's config struct and fill in generic fields.
 */
static struct config_generic *
init_custom_variable(const char *name,
                               const char *short_desc,
                               const char *long_desc,
                               GucContext context,
                               int flags,
                               enum config_type type,
                               size_t sz)
{
      struct config_generic *gen;

      /*
       * Only allow custom PGC_POSTMASTER variables to be created during shared
       * library preload; any later than that, we can't ensure that the value
       * doesn't change after startup.  This is a fatal elog if it happens; just
       * erroring out isn't safe because we don't know what the calling loadable
       * module might already have hooked into.
       */
      if (context == PGC_POSTMASTER &&
            !process_shared_preload_libraries_in_progress)
            elog(FATAL, "cannot create PGC_POSTMASTER variables after startup");

      gen = (struct config_generic *) guc_malloc(ERROR, sz);
      memset(gen, 0, sz);

      gen->name = guc_strdup(ERROR, name);
      gen->context = context;
      gen->group = CUSTOM_OPTIONS;
      gen->short_desc = short_desc;
      gen->long_desc = long_desc;
      gen->flags = flags;
      gen->vartype = type;

      return gen;
}

/*
 * Common code for DefineCustomXXXVariable subroutines: insert the new
 * variable into the GUC variable array, replacing any placeholder.
 */
static void
define_custom_variable(struct config_generic * variable)
{
      const char *name = variable->name;
      const char **nameAddr = &name;
      const char *value;
      struct config_string *pHolder;
      GucContext  phcontext;
      struct config_generic **res;

      /*
       * See if there's a placeholder by the same name.
       */
      res = (struct config_generic **) bsearch((void *) &nameAddr,
                                                                   (void *) guc_variables,
                                                                   num_guc_variables,
                                                                   sizeof(struct config_generic *),
                                                                   guc_var_compare);
      if (res == NULL)
      {
            /*
             * No placeholder to replace, so we can just add it ... but first,
             * make sure it's initialized to its default value.
             */
            InitializeOneGUCOption(variable);
            add_guc_variable(variable, ERROR);
            return;
      }

      /*
       * This better be a placeholder
       */
      if (((*res)->flags & GUC_CUSTOM_PLACEHOLDER) == 0)
            ereport(ERROR,
                        (errcode(ERRCODE_INTERNAL_ERROR),
                         errmsg("attempt to redefine parameter \"%s\"", name)));

      Assert((*res)->vartype == PGC_STRING);
      pHolder = (struct config_string *) (*res);

      /*
       * First, set the variable to its default value.  We must do this even
       * though we intend to immediately apply a new value, since it's possible
       * that the new value is invalid.
       */
      InitializeOneGUCOption(variable);

      /*
       * Replace the placeholder. We aren't changing the name, so no re-sorting
       * is necessary
       */
      *res = variable;

      /*
       * Infer context for assignment based on source of existing value. We
       * can't tell this with exact accuracy, but we can at least do something
       * reasonable in typical cases.
       */
      switch (pHolder->gen.source)
      {
            case PGC_S_DEFAULT:
            case PGC_S_ENV_VAR:
            case PGC_S_FILE:
            case PGC_S_ARGV:

                  /*
                   * If we got past the check in init_custom_variable, we can safely
                   * assume that any existing value for a PGC_POSTMASTER variable
                   * was set in postmaster context.
                   */
                  if (variable->context == PGC_POSTMASTER)
                        phcontext = PGC_POSTMASTER;
                  else
                        phcontext = PGC_SIGHUP;
                  break;
            case PGC_S_DATABASE:
            case PGC_S_USER:
            case PGC_S_CLIENT:
            case PGC_S_SESSION:
            default:
                  phcontext = PGC_USERSET;
                  break;
      }

      /*
       * Assign the string value stored in the placeholder to the real variable.
       *
       * XXX this is not really good enough --- it should be a nontransactional
       * assignment, since we don't want it to roll back if the current xact
       * fails later.  (Or do we?)
       */
      value = *pHolder->variable;

      if (value)
      {
            if (set_config_option(name, value,
                                            phcontext, pHolder->gen.source,
                                            GUC_ACTION_SET, true))
            {
                  /* Also copy over any saved source-location information */
                  if (pHolder->gen.sourcefile)
                        set_config_sourcefile(name, pHolder->gen.sourcefile,
                                                        pHolder->gen.sourceline);
            }
      }

      /*
       * Free up as much as we conveniently can of the placeholder structure
       * (this neglects any stack items...)
       */
      set_string_field(pHolder, pHolder->variable, NULL);
      set_string_field(pHolder, &pHolder->reset_val, NULL);

      free(pHolder);
}

void
DefineCustomBoolVariable(const char *name,
                                     const char *short_desc,
                                     const char *long_desc,
                                     bool *valueAddr,
                                     bool bootValue,
                                     GucContext context,
                                     int flags,
                                     GucBoolAssignHook assign_hook,
                                     GucShowHook show_hook)
{
      struct config_bool *var;

      var = (struct config_bool *)
            init_custom_variable(name, short_desc, long_desc, context, flags,
                                           PGC_BOOL, sizeof(struct config_bool));
      var->variable = valueAddr;
      var->boot_val = bootValue;
      var->reset_val = bootValue;
      var->assign_hook = assign_hook;
      var->show_hook = show_hook;
      define_custom_variable(&var->gen);
}

void
DefineCustomIntVariable(const char *name,
                                    const char *short_desc,
                                    const char *long_desc,
                                    int *valueAddr,
                                    int bootValue,
                                    int minValue,
                                    int maxValue,
                                    GucContext context,
                                    int flags,
                                    GucIntAssignHook assign_hook,
                                    GucShowHook show_hook)
{
      struct config_int *var;

      var = (struct config_int *)
            init_custom_variable(name, short_desc, long_desc, context, flags,
                                           PGC_INT, sizeof(struct config_int));
      var->variable = valueAddr;
      var->boot_val = bootValue;
      var->reset_val = bootValue;
      var->min = minValue;
      var->max = maxValue;
      var->assign_hook = assign_hook;
      var->show_hook = show_hook;
      define_custom_variable(&var->gen);
}

void
DefineCustomRealVariable(const char *name,
                                     const char *short_desc,
                                     const char *long_desc,
                                     double *valueAddr,
                                     double bootValue,
                                     double minValue,
                                     double maxValue,
                                     GucContext context,
                                     int flags,
                                     GucRealAssignHook assign_hook,
                                     GucShowHook show_hook)
{
      struct config_real *var;

      var = (struct config_real *)
            init_custom_variable(name, short_desc, long_desc, context, flags,
                                           PGC_REAL, sizeof(struct config_real));
      var->variable = valueAddr;
      var->boot_val = bootValue;
      var->reset_val = bootValue;
      var->min = minValue;
      var->max = maxValue;
      var->assign_hook = assign_hook;
      var->show_hook = show_hook;
      define_custom_variable(&var->gen);
}

void
DefineCustomStringVariable(const char *name,
                                       const char *short_desc,
                                       const char *long_desc,
                                       char **valueAddr,
                                       const char *bootValue,
                                       GucContext context,
                                       int flags,
                                       GucStringAssignHook assign_hook,
                                       GucShowHook show_hook)
{
      struct config_string *var;

      var = (struct config_string *)
            init_custom_variable(name, short_desc, long_desc, context, flags,
                                           PGC_STRING, sizeof(struct config_string));
      var->variable = valueAddr;
      var->boot_val = bootValue;
      /* we could probably do without strdup, but keep it like normal case */
      if (var->boot_val)
            var->reset_val = guc_strdup(ERROR, var->boot_val);
      var->assign_hook = assign_hook;
      var->show_hook = show_hook;
      define_custom_variable(&var->gen);
}

void
DefineCustomEnumVariable(const char *name,
                                     const char *short_desc,
                                     const char *long_desc,
                                     int *valueAddr,
                                     int bootValue,
                                     const struct config_enum_entry * options,
                                     GucContext context,
                                     int flags,
                                     GucEnumAssignHook assign_hook,
                                     GucShowHook show_hook)
{
      struct config_enum *var;

      var = (struct config_enum *)
            init_custom_variable(name, short_desc, long_desc, context, flags,
                                           PGC_ENUM, sizeof(struct config_enum));
      var->variable = valueAddr;
      var->boot_val = bootValue;
      var->reset_val = bootValue;
      var->options = options;
      var->assign_hook = assign_hook;
      var->show_hook = show_hook;
      define_custom_variable(&var->gen);
}

void
EmitWarningsOnPlaceholders(const char *className)
{
      int               classLen = strlen(className);
      int               i;

      for (i = 0; i < num_guc_variables; i++)
      {
            struct config_generic *var = guc_variables[i];

            if ((var->flags & GUC_CUSTOM_PLACEHOLDER) != 0 &&
                  strncmp(className, var->name, classLen) == 0 &&
                  var->name[classLen] == GUC_QUALIFIER_SEPARATOR)
            {
                  ereport(WARNING,
                              (errcode(ERRCODE_UNDEFINED_OBJECT),
                               errmsg("unrecognized configuration parameter \"%s\"",
                                          var->name)));
            }
      }
}


/*
 * SHOW command
 */
void
GetPGVariable(const char *name, DestReceiver *dest)
{
      if (guc_name_compare(name, "all") == 0)
            ShowAllGUCConfig(dest);
      else
            ShowGUCConfigOption(name, dest);
}

TupleDesc
GetPGVariableResultDesc(const char *name)
{
      TupleDesc   tupdesc;

      if (guc_name_compare(name, "all") == 0)
      {
            /* need a tuple descriptor representing three TEXT columns */
            tupdesc = CreateTemplateTupleDesc(3, false);
            TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 2, "setting",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 3, "description",
                                       TEXTOID, -1, 0);
      }
      else
      {
            const char *varname;

            /* Get the canonical spelling of name */
            (void) GetConfigOptionByName(name, &varname);

            /* need a tuple descriptor representing a single TEXT column */
            tupdesc = CreateTemplateTupleDesc(1, false);
            TupleDescInitEntry(tupdesc, (AttrNumber) 1, varname,
                                       TEXTOID, -1, 0);
      }
      return tupdesc;
}


/*
 * SHOW command
 */
static void
ShowGUCConfigOption(const char *name, DestReceiver *dest)
{
      TupOutputState *tstate;
      TupleDesc   tupdesc;
      const char *varname;
      char     *value;

      /* Get the value and canonical spelling of name */
      value = GetConfigOptionByName(name, &varname);

      /* need a tuple descriptor representing a single TEXT column */
      tupdesc = CreateTemplateTupleDesc(1, false);
      TupleDescInitEntry(tupdesc, (AttrNumber) 1, varname,
                                 TEXTOID, -1, 0);

      /* prepare for projection of tuples */
      tstate = begin_tup_output_tupdesc(dest, tupdesc);

      /* Send it */
      do_text_output_oneline(tstate, value);

      end_tup_output(tstate);
}

/*
 * SHOW ALL command
 */
static void
ShowAllGUCConfig(DestReceiver *dest)
{
      bool        am_superuser = superuser();
      int               i;
      TupOutputState *tstate;
      TupleDesc   tupdesc;
      char     *values[3];

      /* need a tuple descriptor representing three TEXT columns */
      tupdesc = CreateTemplateTupleDesc(3, false);
      TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
                                 TEXTOID, -1, 0);
      TupleDescInitEntry(tupdesc, (AttrNumber) 2, "setting",
                                 TEXTOID, -1, 0);
      TupleDescInitEntry(tupdesc, (AttrNumber) 3, "description",
                                 TEXTOID, -1, 0);


      /* prepare for projection of tuples */
      tstate = begin_tup_output_tupdesc(dest, tupdesc);

      for (i = 0; i < num_guc_variables; i++)
      {
            struct config_generic *conf = guc_variables[i];

            if ((conf->flags & GUC_NO_SHOW_ALL) ||
                  ((conf->flags & GUC_SUPERUSER_ONLY) && !am_superuser))
                  continue;

            /* assign to the values array */
            values[0] = (char *) conf->name;
            values[1] = _ShowOption(conf, true);
            values[2] = (char *) conf->short_desc;

            /* send it to dest */
            do_tup_output(tstate, values);

            /* clean up */
            if (values[1] != NULL)
                  pfree(values[1]);
      }

      end_tup_output(tstate);
}

/*
 * Return GUC variable value by name; optionally return canonical
 * form of name.  Return value is palloc'd.
 */
char *
GetConfigOptionByName(const char *name, const char **varname)
{
      struct config_generic *record;

      record = find_option(name, false, ERROR);
      if (record == NULL)
            ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("unrecognized configuration parameter \"%s\"", name)));
      if ((record->flags & GUC_SUPERUSER_ONLY) && !superuser())
            ereport(ERROR,
                        (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                         errmsg("must be superuser to examine \"%s\"", name)));

      if (varname)
            *varname = record->name;

      return _ShowOption(record, true);
}

/*
 * Return GUC variable value by variable number; optionally return canonical
 * form of name.  Return value is palloc'd.
 */
void
GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
{
      char        buffer[256];
      struct config_generic *conf;

      /* check requested variable number valid */
      Assert((varnum >= 0) && (varnum < num_guc_variables));

      conf = guc_variables[varnum];

      if (noshow)
      {
            if ((conf->flags & GUC_NO_SHOW_ALL) ||
                  ((conf->flags & GUC_SUPERUSER_ONLY) && !superuser()))
                  *noshow = true;
            else
                  *noshow = false;
      }

      /* first get the generic attributes */

      /* name */
      values[0] = conf->name;

      /* setting : use _ShowOption in order to avoid duplicating the logic */
      values[1] = _ShowOption(conf, false);

      /* unit */
      if (conf->vartype == PGC_INT)
      {
            static char buf[8];

            switch (conf->flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME))
            {
                  case GUC_UNIT_KB:
                        values[2] = "kB";
                        break;
                  case GUC_UNIT_BLOCKS:
                        snprintf(buf, sizeof(buf), "%dkB", BLCKSZ / 1024);
                        values[2] = buf;
                        break;
                  case GUC_UNIT_XBLOCKS:
                        snprintf(buf, sizeof(buf), "%dkB", XLOG_BLCKSZ / 1024);
                        values[2] = buf;
                        break;
                  case GUC_UNIT_MS:
                        values[2] = "ms";
                        break;
                  case GUC_UNIT_S:
                        values[2] = "s";
                        break;
                  case GUC_UNIT_MIN:
                        values[2] = "min";
                        break;
                  default:
                        values[2] = "";
                        break;
            }
      }
      else
            values[2] = NULL;

      /* group */
      values[3] = config_group_names[conf->group];

      /* short_desc */
      values[4] = conf->short_desc;

      /* extra_desc */
      values[5] = conf->long_desc;

      /* context */
      values[6] = GucContext_Names[conf->context];

      /* vartype */
      values[7] = config_type_names[conf->vartype];

      /* source */
      values[8] = GucSource_Names[conf->source];

      /* now get the type specifc attributes */
      switch (conf->vartype)
      {
            case PGC_BOOL:
                  {
                        struct config_bool *lconf = (struct config_bool *) conf;

                        /* min_val */
                        values[9] = NULL;

                        /* max_val */
                        values[10] = NULL;

                        /* enumvals */
                        values[11] = NULL;

                        /* boot_val */
                        values[12] = pstrdup(lconf->boot_val ? "on" : "off");

                        /* reset_val */
                        values[13] = pstrdup(lconf->reset_val ? "on" : "off");
                  }
                  break;

            case PGC_INT:
                  {
                        struct config_int *lconf = (struct config_int *) conf;

                        /* min_val */
                        snprintf(buffer, sizeof(buffer), "%d", lconf->min);
                        values[9] = pstrdup(buffer);

                        /* max_val */
                        snprintf(buffer, sizeof(buffer), "%d", lconf->max);
                        values[10] = pstrdup(buffer);

                        /* enumvals */
                        values[11] = NULL;

                        /* boot_val */
                        snprintf(buffer, sizeof(buffer), "%d", lconf->boot_val);
                        values[12] = pstrdup(buffer);

                        /* reset_val */
                        snprintf(buffer, sizeof(buffer), "%d", lconf->reset_val);
                        values[13] = pstrdup(buffer);
                  }
                  break;

            case PGC_REAL:
                  {
                        struct config_real *lconf = (struct config_real *) conf;

                        /* min_val */
                        snprintf(buffer, sizeof(buffer), "%g", lconf->min);
                        values[9] = pstrdup(buffer);

                        /* max_val */
                        snprintf(buffer, sizeof(buffer), "%g", lconf->max);
                        values[10] = pstrdup(buffer);

                        /* enumvals */
                        values[11] = NULL;

                        /* boot_val */
                        snprintf(buffer, sizeof(buffer), "%g", lconf->boot_val);
                        values[12] = pstrdup(buffer);

                        /* reset_val */
                        snprintf(buffer, sizeof(buffer), "%g", lconf->reset_val);
                        values[13] = pstrdup(buffer);
                  }
                  break;

            case PGC_STRING:
                  {
                        struct config_string *lconf = (struct config_string *) conf;

                        /* min_val */
                        values[9] = NULL;

                        /* max_val */
                        values[10] = NULL;

                        /* enumvals */
                        values[11] = NULL;

                        /* boot_val */
                        if (lconf->boot_val == NULL)
                              values[12] = NULL;
                        else
                              values[12] = pstrdup(lconf->boot_val);

                        /* reset_val */
                        if (lconf->reset_val == NULL)
                              values[13] = NULL;
                        else
                              values[13] = pstrdup(lconf->reset_val);
                  }
                  break;

            case PGC_ENUM:
                  {
                        struct config_enum *lconf = (struct config_enum *) conf;

                        /* min_val */
                        values[9] = NULL;

                        /* max_val */
                        values[10] = NULL;

                        /* enumvals */

                        /*
                         * NOTE! enumvals with double quotes in them are not
                         * supported!
                         */
                        values[11] = config_enum_get_options((struct config_enum *) conf,
                                                                               "{\"", "\"}", "\",\"");

                        /* boot_val */
                        values[12] = pstrdup(config_enum_lookup_by_value(lconf,
                                                                                       lconf->boot_val));

                        /* reset_val */
                        values[13] = pstrdup(config_enum_lookup_by_value(lconf,
                                                                                      lconf->reset_val));
                  }
                  break;

            default:
                  {
                        /*
                         * should never get here, but in case we do, set 'em to NULL
                         */

                        /* min_val */
                        values[9] = NULL;

                        /* max_val */
                        values[10] = NULL;

                        /* enumvals */
                        values[11] = NULL;

                        /* boot_val */
                        values[12] = NULL;

                        /* reset_val */
                        values[13] = NULL;
                  }
                  break;
      }

      /*
       * If the setting came from a config file, set the source location. For
       * security reasons, we don't show source file/line number for
       * non-superusers.
       */
      if (conf->source == PGC_S_FILE && superuser())
      {
            values[14] = conf->sourcefile;
            snprintf(buffer, sizeof(buffer), "%d", conf->sourceline);
            values[15] = pstrdup(buffer);
      }
      else
      {
            values[14] = NULL;
            values[15] = NULL;
      }
}

/*
 * Return the total number of GUC variables
 */
int
GetNumConfigOptions(void)
{
      return num_guc_variables;
}

/*
 * show_config_by_name - equiv to SHOW X command but implemented as
 * a function.
 */
Datum
show_config_by_name(PG_FUNCTION_ARGS)
{
      char     *varname;
      char     *varval;

      /* Get the GUC variable name */
      varname = TextDatumGetCString(PG_GETARG_DATUM(0));

      /* Get the value */
      varval = GetConfigOptionByName(varname, NULL);

      /* Convert to text */
      PG_RETURN_TEXT_P(cstring_to_text(varval));
}

/*
 * show_all_settings - equiv to SHOW ALL command but implemented as
 * a Table Function.
 */
#define NUM_PG_SETTINGS_ATTS  16

Datum
show_all_settings(PG_FUNCTION_ARGS)
{
      FuncCallContext *funcctx;
      TupleDesc   tupdesc;
      int               call_cntr;
      int               max_calls;
      AttInMetadata *attinmeta;
      MemoryContext oldcontext;

      /* stuff done only on the first call of the function */
      if (SRF_IS_FIRSTCALL())
      {
            /* create a function context for cross-call persistence */
            funcctx = SRF_FIRSTCALL_INIT();

            /*
             * switch to memory context appropriate for multiple function calls
             */
            oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

            /*
             * need a tuple descriptor representing NUM_PG_SETTINGS_ATTS columns
             * of the appropriate types
             */
            tupdesc = CreateTemplateTupleDesc(NUM_PG_SETTINGS_ATTS, false);
            TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 2, "setting",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 3, "unit",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 4, "category",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 5, "short_desc",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 6, "extra_desc",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 7, "context",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 8, "vartype",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 9, "source",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 10, "min_val",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 11, "max_val",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 12, "enumvals",
                                       TEXTARRAYOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 13, "boot_val",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 14, "reset_val",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 15, "sourcefile",
                                       TEXTOID, -1, 0);
            TupleDescInitEntry(tupdesc, (AttrNumber) 16, "sourceline",
                                       INT4OID, -1, 0);

            /*
             * Generate attribute metadata needed later to produce tuples from raw
             * C strings
             */
            attinmeta = TupleDescGetAttInMetadata(tupdesc);
            funcctx->attinmeta = attinmeta;

            /* total number of tuples to be returned */
            funcctx->max_calls = GetNumConfigOptions();

            MemoryContextSwitchTo(oldcontext);
      }

      /* stuff done on every call of the function */
      funcctx = SRF_PERCALL_SETUP();

      call_cntr = funcctx->call_cntr;
      max_calls = funcctx->max_calls;
      attinmeta = funcctx->attinmeta;

      if (call_cntr < max_calls)    /* do when there is more left to send */
      {
            char     *values[NUM_PG_SETTINGS_ATTS];
            bool        noshow;
            HeapTuple   tuple;
            Datum       result;

            /*
             * Get the next visible GUC variable name and value
             */
            do
            {
                  GetConfigOptionByNum(call_cntr, (const char **) values, &noshow);
                  if (noshow)
                  {
                        /* bump the counter and get the next config setting */
                        call_cntr = ++funcctx->call_cntr;

                        /* make sure we haven't gone too far now */
                        if (call_cntr >= max_calls)
                              SRF_RETURN_DONE(funcctx);
                  }
            } while (noshow);

            /* build a tuple */
            tuple = BuildTupleFromCStrings(attinmeta, values);

            /* make the tuple into a datum */
            result = HeapTupleGetDatum(tuple);

            SRF_RETURN_NEXT(funcctx, result);
      }
      else
      {
            /* do when there is no more left */
            SRF_RETURN_DONE(funcctx);
      }
}

static char *
_ShowOption(struct config_generic * record, bool use_units)
{
      char        buffer[256];
      const char *val;

      switch (record->vartype)
      {
            case PGC_BOOL:
                  {
                        struct config_bool *conf = (struct config_bool *) record;

                        if (conf->show_hook)
                              val = (*conf->show_hook) ();
                        else
                              val = *conf->variable ? "on" : "off";
                  }
                  break;

            case PGC_INT:
                  {
                        struct config_int *conf = (struct config_int *) record;

                        if (conf->show_hook)
                              val = (*conf->show_hook) ();
                        else
                        {
                              /*
                               * Use int64 arithmetic to avoid overflows in units
                               * conversion.    If INT64_IS_BUSTED we might overflow
                               * anyway and print bogus answers, but there are few
                               * enough such machines that it doesn't seem worth trying
                               * harder.
                               */
                              int64       result = *conf->variable;
                              const char *unit;

                              if (use_units && result > 0 &&
                                    (record->flags & GUC_UNIT_MEMORY))
                              {
                                    switch (record->flags & GUC_UNIT_MEMORY)
                                    {
                                          case GUC_UNIT_BLOCKS:
                                                result *= BLCKSZ / 1024;
                                                break;
                                          case GUC_UNIT_XBLOCKS:
                                                result *= XLOG_BLCKSZ / 1024;
                                                break;
                                    }

                                    if (result % KB_PER_GB == 0)
                                    {
                                          result /= KB_PER_GB;
                                          unit = "GB";
                                    }
                                    else if (result % KB_PER_MB == 0)
                                    {
                                          result /= KB_PER_MB;
                                          unit = "MB";
                                    }
                                    else
                                    {
                                          unit = "kB";
                                    }
                              }
                              else if (use_units && result > 0 &&
                                           (record->flags & GUC_UNIT_TIME))
                              {
                                    switch (record->flags & GUC_UNIT_TIME)
                                    {
                                          case GUC_UNIT_S:
                                                result *= MS_PER_S;
                                                break;
                                          case GUC_UNIT_MIN:
                                                result *= MS_PER_MIN;
                                                break;
                                    }

                                    if (result % MS_PER_D == 0)
                                    {
                                          result /= MS_PER_D;
                                          unit = "d";
                                    }
                                    else if (result % MS_PER_H == 0)
                                    {
                                          result /= MS_PER_H;
                                          unit = "h";
                                    }
                                    else if (result % MS_PER_MIN == 0)
                                    {
                                          result /= MS_PER_MIN;
                                          unit = "min";
                                    }
                                    else if (result % MS_PER_S == 0)
                                    {
                                          result /= MS_PER_S;
                                          unit = "s";
                                    }
                                    else
                                    {
                                          unit = "ms";
                                    }
                              }
                              else
                                    unit = "";

                              snprintf(buffer, sizeof(buffer), INT64_FORMAT "%s",
                                           result, unit);
                              val = buffer;
                        }
                  }
                  break;

            case PGC_REAL:
                  {
                        struct config_real *conf = (struct config_real *) record;

                        if (conf->show_hook)
                              val = (*conf->show_hook) ();
                        else
                        {
                              snprintf(buffer, sizeof(buffer), "%g",
                                           *conf->variable);
                              val = buffer;
                        }
                  }
                  break;

            case PGC_STRING:
                  {
                        struct config_string *conf = (struct config_string *) record;

                        if (conf->show_hook)
                              val = (*conf->show_hook) ();
                        else if (*conf->variable && **conf->variable)
                              val = *conf->variable;
                        else
                              val = "";
                  }
                  break;

            case PGC_ENUM:
                  {
                        struct config_enum *conf = (struct config_enum *) record;

                        if (conf->show_hook)
                              val = (*conf->show_hook) ();
                        else
                              val = config_enum_lookup_by_value(conf, *conf->variable);
                  }
                  break;

            default:
                  /* just to keep compiler quiet */
                  val = "???";
                  break;
      }

      return pstrdup(val);
}


/*
 * Attempt (badly) to detect if a proposed new GUC setting is the same
 * as the current value.
 *
 * XXX this does not really work because it doesn't account for the
 * effects of canonicalization of string values by assign_hooks.
 */
static bool
is_newvalue_equal(struct config_generic * record, const char *newvalue)
{
      /* newvalue == NULL isn't supported */
      Assert(newvalue != NULL);

      switch (record->vartype)
      {
            case PGC_BOOL:
                  {
                        struct config_bool *conf = (struct config_bool *) record;
                        bool        newval;

                        return parse_bool(newvalue, &newval)
                              && *conf->variable == newval;
                  }
            case PGC_INT:
                  {
                        struct config_int *conf = (struct config_int *) record;
                        int               newval;

                        return parse_int(newvalue, &newval, record->flags, NULL)
                              && *conf->variable == newval;
                  }
            case PGC_REAL:
                  {
                        struct config_real *conf = (struct config_real *) record;
                        double            newval;

                        return parse_real(newvalue, &newval)
                              && *conf->variable == newval;
                  }
            case PGC_STRING:
                  {
                        struct config_string *conf = (struct config_string *) record;

                        return *conf->variable != NULL &&
                              strcmp(*conf->variable, newvalue) == 0;
                  }

            case PGC_ENUM:
                  {
                        struct config_enum *conf = (struct config_enum *) record;
                        int               newval;

                        return config_enum_lookup_by_name(conf, newvalue, &newval) &&
                              *conf->variable == newval;
                  }
      }

      return false;
}


#ifdef EXEC_BACKEND

/*
 *    These routines dump out all non-default GUC options into a binary
 *    file that is read by all exec'ed backends.  The format is:
 *
 *          variable name, string, null terminated
 *          variable value, string, null terminated
 *          variable source, integer
 */
static void
write_one_nondefault_variable(FILE *fp, struct config_generic * gconf)
{
      if (gconf->source == PGC_S_DEFAULT)
            return;

      fprintf(fp, "%s", gconf->name);
      fputc(0, fp);

      switch (gconf->vartype)
      {
            case PGC_BOOL:
                  {
                        struct config_bool *conf = (struct config_bool *) gconf;

                        if (*conf->variable)
                              fprintf(fp, "true");
                        else
                              fprintf(fp, "false");
                  }
                  break;

            case PGC_INT:
                  {
                        struct config_int *conf = (struct config_int *) gconf;

                        fprintf(fp, "%d", *conf->variable);
                  }
                  break;

            case PGC_REAL:
                  {
                        struct config_real *conf = (struct config_real *) gconf;

                        /* Could lose precision here? */
                        fprintf(fp, "%f", *conf->variable);
                  }
                  break;

            case PGC_STRING:
                  {
                        struct config_string *conf = (struct config_string *) gconf;

                        fprintf(fp, "%s", *conf->variable);
                  }
                  break;

            case PGC_ENUM:
                  {
                        struct config_enum *conf = (struct config_enum *) gconf;

                        fprintf(fp, "%s",
                                    config_enum_lookup_by_value(conf, *conf->variable));
                  }
                  break;
      }

      fputc(0, fp);

      fwrite(&gconf->source, sizeof(gconf->source), 1, fp);
}

void
write_nondefault_variables(GucContext context)
{
      int               elevel;
      FILE     *fp;
      struct config_generic *cvc_conf;
      int               i;

      Assert(context == PGC_POSTMASTER || context == PGC_SIGHUP);

      elevel = (context == PGC_SIGHUP) ? LOG : ERROR;

      /*
       * Open file
       */
      fp = AllocateFile(CONFIG_EXEC_PARAMS_NEW, "w");
      if (!fp)
      {
            ereport(elevel,
                        (errcode_for_file_access(),
                         errmsg("could not write to file \"%s\": %m",
                                    CONFIG_EXEC_PARAMS_NEW)));
            return;
      }

      /*
       * custom_variable_classes must be written out first; otherwise we might
       * reject custom variable values while reading the file.
       */
      cvc_conf = find_option("custom_variable_classes", false, ERROR);
      if (cvc_conf)
            write_one_nondefault_variable(fp, cvc_conf);

      for (i = 0; i < num_guc_variables; i++)
      {
            struct config_generic *gconf = guc_variables[i];

            if (gconf != cvc_conf)
                  write_one_nondefault_variable(fp, gconf);
      }

      if (FreeFile(fp))
      {
            ereport(elevel,
                        (errcode_for_file_access(),
                         errmsg("could not write to file \"%s\": %m",
                                    CONFIG_EXEC_PARAMS_NEW)));
            return;
      }

      /*
       * Put new file in place.  This could delay on Win32, but we don't hold
       * any exclusive locks.
       */
      rename(CONFIG_EXEC_PARAMS_NEW, CONFIG_EXEC_PARAMS);
}


/*
 *    Read string, including null byte from file
 *
 *    Return NULL on EOF and nothing read
 */
static char *
read_string_with_null(FILE *fp)
{
      int               i = 0,
                        ch,
                        maxlen = 256;
      char     *str = NULL;

      do
      {
            if ((ch = fgetc(fp)) == EOF)
            {
                  if (i == 0)
                        return NULL;
                  else
                        elog(FATAL, "invalid format of exec config params file");
            }
            if (i == 0)
                  str = guc_malloc(FATAL, maxlen);
            else if (i == maxlen)
                  str = guc_realloc(FATAL, str, maxlen *= 2);
            str[i++] = ch;
      } while (ch != 0);

      return str;
}


/*
 *    This routine loads a previous postmaster dump of its non-default
 *    settings.
 */
void
read_nondefault_variables(void)
{
      FILE     *fp;
      char     *varname,
                     *varvalue;
      int               varsource;

      /*
       * Open file
       */
      fp = AllocateFile(CONFIG_EXEC_PARAMS, "r");
      if (!fp)
      {
            /* File not found is fine */
            if (errno != ENOENT)
                  ereport(FATAL,
                              (errcode_for_file_access(),
                               errmsg("could not read from file \"%s\": %m",
                                          CONFIG_EXEC_PARAMS)));
            return;
      }

      for (;;)
      {
            struct config_generic *record;

            if ((varname = read_string_with_null(fp)) == NULL)
                  break;

            if ((record = find_option(varname, true, FATAL)) == NULL)
                  elog(FATAL, "failed to locate variable %s in exec config params file", varname);
            if ((varvalue = read_string_with_null(fp)) == NULL)
                  elog(FATAL, "invalid format of exec config params file");
            if (fread(&varsource, sizeof(varsource), 1, fp) == 0)
                  elog(FATAL, "invalid format of exec config params file");

            (void) set_config_option(varname, varvalue, record->context,
                                                 varsource, GUC_ACTION_SET, true);
            free(varname);
            free(varvalue);
      }

      FreeFile(fp);
}
#endif   /* EXEC_BACKEND */


/*
 * A little "long argument" simulation, although not quite GNU
 * compliant. Takes a string of the form "some-option=some value" and
 * returns name = "some_option" and value = "some value" in malloc'ed
 * storage. Note that '-' is converted to '_' in the option name. If
 * there is no '=' in the input string then value will be NULL.
 */
void
ParseLongOption(const char *string, char **name, char **value)
{
      size_t            equal_pos;
      char     *cp;

      AssertArg(string);
      AssertArg(name);
      AssertArg(value);

      equal_pos = strcspn(string, "=");

      if (string[equal_pos] == '=')
      {
            *name = guc_malloc(FATAL, equal_pos + 1);
            strlcpy(*name, string, equal_pos + 1);

            *value = guc_strdup(FATAL, &string[equal_pos + 1]);
      }
      else
      {
            /* no equal sign in string */
            *name = guc_strdup(FATAL, string);
            *value = NULL;
      }

      for (cp = *name; *cp; cp++)
            if (*cp == '-')
                  *cp = '_';
}


/*
 * Handle options fetched from pg_database.datconfig, pg_authid.rolconfig,
 * pg_proc.proconfig, etc.    Caller must specify proper context/source/action.
 *
 * The array parameter must be an array of TEXT (it must not be NULL).
 */
void
ProcessGUCArray(ArrayType *array,
                        GucContext context, GucSource source, GucAction action)
{
      int               i;

      Assert(array != NULL);
      Assert(ARR_ELEMTYPE(array) == TEXTOID);
      Assert(ARR_NDIM(array) == 1);
      Assert(ARR_LBOUND(array)[0] == 1);

      for (i = 1; i <= ARR_DIMS(array)[0]; i++)
      {
            Datum       d;
            bool        isnull;
            char     *s;
            char     *name;
            char     *value;

            d = array_ref(array, 1, &i,
                                -1 /* varlenarray */ ,
                                -1 /* TEXT's typlen */ ,
                                false /* TEXT's typbyval */ ,
                                'i' /* TEXT's typalign */ ,
                                &isnull);

            if (isnull)
                  continue;

            s = TextDatumGetCString(d);

            ParseLongOption(s, &name, &value);
            if (!value)
            {
                  ereport(WARNING,
                              (errcode(ERRCODE_SYNTAX_ERROR),
                               errmsg("could not parse setting for parameter \"%s\"",
                                          name)));
                  free(name);
                  continue;
            }

            (void) set_config_option(name, value, context, source, action, true);

            free(name);
            if (value)
                  free(value);
      }
}


/*
 * Add an entry to an option array.  The array parameter may be NULL
 * to indicate the current table entry is NULL.
 */
ArrayType *
GUCArrayAdd(ArrayType *array, const char *name, const char *value)
{
      const char *varname;
      Datum       datum;
      char     *newval;
      ArrayType  *a;

      Assert(name);
      Assert(value);

      /* test if the option is valid */
      set_config_option(name, value,
                                superuser() ? PGC_SUSET : PGC_USERSET,
                                PGC_S_TEST, GUC_ACTION_SET, false);

      /* convert name to canonical spelling, so we can use plain strcmp */
      (void) GetConfigOptionByName(name, &varname);
      name = varname;

      newval = palloc(strlen(name) + 1 + strlen(value) + 1);
      sprintf(newval, "%s=%s", name, value);
      datum = CStringGetTextDatum(newval);

      if (array)
      {
            int               index;
            bool        isnull;
            int               i;

            Assert(ARR_ELEMTYPE(array) == TEXTOID);
            Assert(ARR_NDIM(array) == 1);
            Assert(ARR_LBOUND(array)[0] == 1);

            index = ARR_DIMS(array)[0] + 1; /* add after end */

            for (i = 1; i <= ARR_DIMS(array)[0]; i++)
            {
                  Datum       d;
                  char     *current;

                  d = array_ref(array, 1, &i,
                                      -1 /* varlenarray */ ,
                                      -1 /* TEXT's typlen */ ,
                                      false /* TEXT's typbyval */ ,
                                      'i' /* TEXT's typalign */ ,
                                      &isnull);
                  if (isnull)
                        continue;
                  current = TextDatumGetCString(d);
                  if (strncmp(current, newval, strlen(name) + 1) == 0)
                  {
                        index = i;
                        break;
                  }
            }

            a = array_set(array, 1, &index,
                                datum,
                                false,
                                -1 /* varlena array */ ,
                                -1 /* TEXT's typlen */ ,
                                false /* TEXT's typbyval */ ,
                                'i' /* TEXT's typalign */ );
      }
      else
            a = construct_array(&datum, 1,
                                          TEXTOID,
                                          -1, false, 'i');

      return a;
}


/*
 * Delete an entry from an option array.  The array parameter may be NULL
 * to indicate the current table entry is NULL.  Also, if the return value
 * is NULL then a null should be stored.
 */
ArrayType *
GUCArrayDelete(ArrayType *array, const char *name)
{
      const char *varname;
      ArrayType  *newarray;
      int               i;
      int               index;

      Assert(name);

      /* test if the option is valid */
      set_config_option(name, NULL,
                                superuser() ? PGC_SUSET : PGC_USERSET,
                                PGC_S_TEST, GUC_ACTION_SET, false);

      /* convert name to canonical spelling, so we can use plain strcmp */
      (void) GetConfigOptionByName(name, &varname);
      name = varname;

      /* if array is currently null, then surely nothing to delete */
      if (!array)
            return NULL;

      newarray = NULL;
      index = 1;

      for (i = 1; i <= ARR_DIMS(array)[0]; i++)
      {
            Datum       d;
            char     *val;
            bool        isnull;

            d = array_ref(array, 1, &i,
                                -1 /* varlenarray */ ,
                                -1 /* TEXT's typlen */ ,
                                false /* TEXT's typbyval */ ,
                                'i' /* TEXT's typalign */ ,
                                &isnull);
            if (isnull)
                  continue;
            val = TextDatumGetCString(d);

            /* ignore entry if it's what we want to delete */
            if (strncmp(val, name, strlen(name)) == 0
                  && val[strlen(name)] == '=')
                  continue;

            /* else add it to the output array */
            if (newarray)
            {
                  newarray = array_set(newarray, 1, &index,
                                                 d,
                                                 false,
                                                 -1 /* varlenarray */ ,
                                                 -1 /* TEXT's typlen */ ,
                                                 false /* TEXT's typbyval */ ,
                                                 'i' /* TEXT's typalign */ );
            }
            else
                  newarray = construct_array(&d, 1,
                                                         TEXTOID,
                                                         -1, false, 'i');

            index++;
      }

      return newarray;
}


/*
 * assign_hook and show_hook subroutines
 */

static const char *
assign_log_destination(const char *value, bool doit, GucSource source)
{
      char     *rawstring;
      List     *elemlist;
      ListCell   *l;
      int               newlogdest = 0;

      /* Need a modifiable copy of string */
      rawstring = pstrdup(value);

      /* Parse string into list of identifiers */
      if (!SplitIdentifierString(rawstring, ',', &elemlist))
      {
            /* syntax error in list */
            pfree(rawstring);
            list_free(elemlist);
            ereport(GUC_complaint_elevel(source),
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
               errmsg("invalid list syntax for parameter \"log_destination\"")));
            return NULL;
      }

      foreach(l, elemlist)
      {
            char     *tok = (char *) lfirst(l);

            if (pg_strcasecmp(tok, "stderr") == 0)
                  newlogdest |= LOG_DESTINATION_STDERR;
            else if (pg_strcasecmp(tok, "csvlog") == 0)
                  newlogdest |= LOG_DESTINATION_CSVLOG;
#ifdef HAVE_SYSLOG
            else if (pg_strcasecmp(tok, "syslog") == 0)
                  newlogdest |= LOG_DESTINATION_SYSLOG;
#endif
#ifdef WIN32
            else if (pg_strcasecmp(tok, "eventlog") == 0)
                  newlogdest |= LOG_DESTINATION_EVENTLOG;
#endif
            else
            {
                  ereport(GUC_complaint_elevel(source),
                              (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                          errmsg("unrecognized \"log_destination\" key word: \"%s\"",
                                     tok)));
                  pfree(rawstring);
                  list_free(elemlist);
                  return NULL;
            }
      }

      if (doit)
            Log_destination = newlogdest;

      pfree(rawstring);
      list_free(elemlist);

      return value;
}

#ifdef HAVE_SYSLOG

static bool
assign_syslog_facility(int newval, bool doit, GucSource source)
{
      if (doit)
            set_syslog_parameters(syslog_ident_str ? syslog_ident_str : "postgres",
                                            newval);

      return true;
}

static const char *
assign_syslog_ident(const char *ident, bool doit, GucSource source)
{
      if (doit)
            set_syslog_parameters(ident, syslog_facility);

      return ident;
}
#endif   /* HAVE_SYSLOG */


static bool
assign_session_replication_role(int newval, bool doit, GucSource source)
{
      /*
       * Must flush the plan cache when changing replication role; but don't
       * flush unnecessarily.
       */
      if (doit && SessionReplicationRole != newval)
      {
            ResetPlanCache();
      }

      return true;
}

static const char *
show_num_temp_buffers(void)
{
      /*
       * We show the GUC var until local buffers have been initialized, and
       * NLocBuffer afterwards.
       */
      static char nbuf[32];

      sprintf(nbuf, "%d", NLocBuffer ? NLocBuffer : num_temp_buffers);
      return nbuf;
}

static bool
assign_phony_autocommit(bool newval, bool doit, GucSource source)
{
      if (!newval)
      {
            ereport(GUC_complaint_elevel(source),
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("SET AUTOCOMMIT TO OFF is no longer supported")));
            return false;
      }
      return true;
}

static const char *
assign_custom_variable_classes(const char *newval, bool doit, GucSource source)
{
      /*
       * Check syntax. newval must be a comma separated list of identifiers.
       * Whitespace is allowed but removed from the result.
       */
      bool        hasSpaceAfterToken = false;
      const char *cp = newval;
      int               symLen = 0;
      char        c;
      StringInfoData buf;

      initStringInfo(&buf);
      while ((c = *cp++) != '\0')
      {
            if (isspace((unsigned char) c))
            {
                  if (symLen > 0)
                        hasSpaceAfterToken = true;
                  continue;
            }

            if (c == ',')
            {
                  if (symLen > 0)         /* terminate identifier */
                  {
                        appendStringInfoChar(&buf, ',');
                        symLen = 0;
                  }
                  hasSpaceAfterToken = false;
                  continue;
            }

            if (hasSpaceAfterToken || !(isalnum((unsigned char) c) || c == '_'))
            {
                  /*
                   * Syntax error due to token following space after token or
                   * non-identifier character
                   */
                  pfree(buf.data);
                  return NULL;
            }
            appendStringInfoChar(&buf, c);
            symLen++;
      }

      /* Remove stray ',' at end */
      if (symLen == 0 && buf.len > 0)
            buf.data[--buf.len] = '\0';

      /* GUC wants the result malloc'd */
      newval = guc_strdup(LOG, buf.data);

      pfree(buf.data);
      return newval;
}

static bool
assign_debug_assertions(bool newval, bool doit, GucSource source)
{
#ifndef USE_ASSERT_CHECKING
      if (newval)
      {
            ereport(GUC_complaint_elevel(source),
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("assertion checking is not supported by this build")));
            return false;
      }
#endif
      return true;
}

static bool
assign_ssl(bool newval, bool doit, GucSource source)
{
#ifndef USE_SSL
      if (newval)
      {
            ereport(GUC_complaint_elevel(source),
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("SSL is not supported by this build")));
            return false;
      }
#endif
      return true;
}

static bool
assign_stage_log_stats(bool newval, bool doit, GucSource source)
{
      if (newval && log_statement_stats)
      {
            ereport(GUC_complaint_elevel(source),
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("cannot enable parameter when \"log_statement_stats\" is true")));
            /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
            if (source != PGC_S_OVERRIDE)
                  return false;
      }
      return true;
}

static bool
assign_log_stats(bool newval, bool doit, GucSource source)
{
      if (newval &&
            (log_parser_stats || log_planner_stats || log_executor_stats))
      {
            ereport(GUC_complaint_elevel(source),
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("cannot enable \"log_statement_stats\" when "
                                    "\"log_parser_stats\", \"log_planner_stats\", "
                                    "or \"log_executor_stats\" is true")));
            /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
            if (source != PGC_S_OVERRIDE)
                  return false;
      }
      return true;
}

static bool
assign_transaction_read_only(bool newval, bool doit, GucSource source)
{
      /* Can't go to r/w mode inside a r/o transaction */
      if (newval == false && XactReadOnly && IsSubTransaction())
      {
            ereport(GUC_complaint_elevel(source),
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("cannot set transaction read-write mode inside a read-only transaction")));
            /* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
            if (source != PGC_S_OVERRIDE)
                  return false;
      }
      return true;
}

static const char *
assign_canonical_path(const char *newval, bool doit, GucSource source)
{
      if (doit)
      {
            char     *canon_val = guc_strdup(ERROR, newval);

            canonicalize_path(canon_val);
            return canon_val;
      }
      else
            return newval;
}

static const char *
assign_timezone_abbreviations(const char *newval, bool doit, GucSource source)
{
      /*
       * The powerup value shown above for timezone_abbreviations is "UNKNOWN".
       * When we see this we just do nothing.  If this value isn't overridden
       * from the config file then pg_timezone_abbrev_initialize() will
       * eventually replace it with "Default".  This hack has two purposes: to
       * avoid wasting cycles loading values that might soon be overridden from
       * the config file, and to avoid trying to read the timezone abbrev files
       * during InitializeGUCOptions().  The latter doesn't work in an
       * EXEC_BACKEND subprocess because my_exec_path hasn't been set yet and so
       * we can't locate PGSHAREDIR.  (Essentially the same hack is used to
       * delay initializing TimeZone ... if we have any more, we should try to
       * clean up and centralize this mechanism ...)
       */
      if (strcmp(newval, "UNKNOWN") == 0)
      {
            return newval;
      }

      /* Loading abbrev file is expensive, so only do it when value changes */
      if (timezone_abbreviations_string == NULL ||
            strcmp(timezone_abbreviations_string, newval) != 0)
      {
            int               elevel;

            /*
             * If reading config file, only the postmaster should bleat loudly
             * about problems.      Otherwise, it's just this one process doing it,
             * and we use WARNING message level.
             */
            if (source == PGC_S_FILE)
                  elevel = IsUnderPostmaster ? DEBUG3 : LOG;
            else
                  elevel = WARNING;
            if (!load_tzoffsets(newval, doit, elevel))
                  return NULL;
      }
      return newval;
}

/*
 * pg_timezone_abbrev_initialize --- set default value if not done already
 *
 * This is called after initial loading of postgresql.conf.  If no
 * timezone_abbreviations setting was found therein, select default.
 */
void
pg_timezone_abbrev_initialize(void)
{
      if (strcmp(timezone_abbreviations_string, "UNKNOWN") == 0)
      {
            SetConfigOption("timezone_abbreviations", "Default",
                                    PGC_POSTMASTER, PGC_S_ARGV);
      }
}

static const char *
show_archive_command(void)
{
      if (XLogArchiveMode)
            return XLogArchiveCommand;
      else
            return "(disabled)";
}

static bool
assign_tcp_keepalives_idle(int newval, bool doit, GucSource source)
{
      if (doit)
            return (pq_setkeepalivesidle(newval, MyProcPort) == STATUS_OK);

      return true;
}

static const char *
show_tcp_keepalives_idle(void)
{
      static char nbuf[16];

      snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivesidle(MyProcPort));
      return nbuf;
}

static bool
assign_tcp_keepalives_interval(int newval, bool doit, GucSource source)
{
      if (doit)
            return (pq_setkeepalivesinterval(newval, MyProcPort) == STATUS_OK);

      return true;
}

static const char *
show_tcp_keepalives_interval(void)
{
      static char nbuf[16];

      snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivesinterval(MyProcPort));
      return nbuf;
}

static bool
assign_tcp_keepalives_count(int newval, bool doit, GucSource source)
{
      if (doit)
            return (pq_setkeepalivescount(newval, MyProcPort) == STATUS_OK);

      return true;
}

static const char *
show_tcp_keepalives_count(void)
{
      static char nbuf[16];

      snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivescount(MyProcPort));
      return nbuf;
}

static bool
assign_maxconnections(int newval, bool doit, GucSource source)
{
      if (newval + autovacuum_max_workers > INT_MAX / 4)
            return false;

      if (doit)
            MaxBackends = newval + autovacuum_max_workers;

      return true;
}

static bool
assign_autovacuum_max_workers(int newval, bool doit, GucSource source)
{
      if (newval + MaxConnections > INT_MAX / 4)
            return false;

      if (doit)
            MaxBackends = newval + MaxConnections;

      return true;
}

static bool
assign_effective_io_concurrency(int newval, bool doit, GucSource source)
{
#ifdef USE_PREFETCH
      double            new_prefetch_pages = 0.0;
      int               i;

      /*----------
       * The user-visible GUC parameter is the number of drives (spindles),
       * which we need to translate to a number-of-pages-to-prefetch target.
       *
       * The expected number of prefetch pages needed to keep N drives busy is:
       *
       * drives |   I/O requests
       * -------+----------------
       *          1 |   1
       *          2 |   2/1 + 2/2 = 3
       *          3 |   3/1 + 3/2 + 3/3 = 5 1/2
       *          4 |   4/1 + 4/2 + 4/3 + 4/4 = 8 1/3
       *          n |   n * H(n)
       *
       * This is called the "coupon collector problem" and H(n) is called the
       * harmonic series.  This could be approximated by n * ln(n), but for
       * reasonable numbers of drives we might as well just compute the series.
       *
       * Alternatively we could set the target to the number of pages necessary
       * so that the expected number of active spindles is some arbitrary
       * percentage of the total.  This sounds the same but is actually slightly
       * different.  The result ends up being ln(1-P)/ln((n-1)/n) where P is
       * that desired fraction.
       *
       * Experimental results show that both of these formulas aren't aggressive
       * enough, but we don't really have any better proposals.
       *
       * Note that if newval = 0 (disabled), we must set target = 0.
       *----------
       */

      for (i = 1; i <= newval; i++)
            new_prefetch_pages += (double) newval / (double) i;

      /* This range check shouldn't fail, but let's be paranoid */
      if (new_prefetch_pages >= 0.0 && new_prefetch_pages < (double) INT_MAX)
      {
            if (doit)
                  target_prefetch_pages = (int) rint(new_prefetch_pages);
            return true;
      }
      else
            return false;
#else
      return true;
#endif   /* USE_PREFETCH */
}

static const char *
assign_pgstat_temp_directory(const char *newval, bool doit, GucSource source)
{
      if (doit)
      {
            char     *canon_val = guc_strdup(ERROR, newval);
            char     *tname;
            char     *fname;

            canonicalize_path(canon_val);

            tname = guc_malloc(ERROR, strlen(canon_val) + 12);          /* /pgstat.tmp */
            sprintf(tname, "%s/pgstat.tmp", canon_val);
            fname = guc_malloc(ERROR, strlen(canon_val) + 13);          /* /pgstat.stat */
            sprintf(fname, "%s/pgstat.stat", canon_val);

            if (pgstat_stat_tmpname)
                  free(pgstat_stat_tmpname);
            pgstat_stat_tmpname = tname;
            if (pgstat_stat_filename)
                  free(pgstat_stat_filename);
            pgstat_stat_filename = fname;

            return canon_val;
      }
      else
            return newval;
}

#include "guc-file.c"

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