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Sourcecode: postgresql-8.4 version File versions

postgres.c

/*-------------------------------------------------------------------------
 *
 * postgres.c
 *      POSTGRES C Backend Interface
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.568 2009/06/18 10:08:08 heikki Exp $
 *
 * NOTES
 *      this is the "main" module of the postgres backend and
 *      hence the main module of the "traffic cop".
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <time.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/socket.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#ifdef HAVE_SYS_RESOURCE_H
#include <sys/time.h>
#include <sys/resource.h>
#endif
#ifdef HAVE_GETOPT_H
#include <getopt.h>
#endif

#ifndef HAVE_GETRUSAGE
#include "rusagestub.h"
#endif

#include "access/printtup.h"
#include "access/xact.h"
#include "catalog/pg_type.h"
#include "commands/async.h"
#include "commands/prepare.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "nodes/print.h"
#include "optimizer/planner.h"
#include "pgstat.h"
#include "pg_trace.h"
#include "parser/analyze.h"
#include "parser/parser.h"
#include "postmaster/autovacuum.h"
#include "rewrite/rewriteHandler.h"
#include "storage/bufmgr.h"
#include "storage/ipc.h"
#include "storage/proc.h"
#include "storage/sinval.h"
#include "tcop/fastpath.h"
#include "tcop/pquery.h"
#include "tcop/tcopprot.h"
#include "tcop/utility.h"
#include "utils/flatfiles.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/ps_status.h"
#include "utils/snapmgr.h"
#include "mb/pg_wchar.h"


extern int  optind;
extern char *optarg;

/* ----------------
 *          global variables
 * ----------------
 */
const char *debug_query_string; /* client-supplied query string */

/* Note: whereToSendOutput is initialized for the bootstrap/standalone case */
CommandDest whereToSendOutput = DestDebug;

/* flag for logging end of session */
bool        Log_disconnections = false;

int               log_statement = LOGSTMT_NONE;

/* GUC variable for maximum stack depth (measured in kilobytes) */
int               max_stack_depth = 100;

/* wait N seconds to allow attach from a debugger */
int               PostAuthDelay = 0;



/* ----------------
 *          private variables
 * ----------------
 */

/* max_stack_depth converted to bytes for speed of checking */
static long max_stack_depth_bytes = 100 * 1024L;

/*
 * Stack base pointer -- initialized by PostgresMain. This is not static
 * so that PL/Java can modify it.
 */
char     *stack_base_ptr = NULL;


/*
 * Flag to mark SIGHUP. Whenever the main loop comes around it
 * will reread the configuration file. (Better than doing the
 * reading in the signal handler, ey?)
 */
static volatile sig_atomic_t got_SIGHUP = false;

/*
 * Flag to keep track of whether we have started a transaction.
 * For extended query protocol this has to be remembered across messages.
 */
static bool xact_started = false;

/*
 * Flag to indicate that we are doing the outer loop's read-from-client,
 * as opposed to any random read from client that might happen within
 * commands like COPY FROM STDIN.
 */
static bool DoingCommandRead = false;

/*
 * Flags to implement skip-till-Sync-after-error behavior for messages of
 * the extended query protocol.
 */
static bool doing_extended_query_message = false;
static bool ignore_till_sync = false;

/*
 * If an unnamed prepared statement exists, it's stored here.
 * We keep it separate from the hashtable kept by commands/prepare.c
 * in order to reduce overhead for short-lived queries.
 */
static CachedPlanSource *unnamed_stmt_psrc = NULL;

/* workspace for building a new unnamed statement in */
static MemoryContext unnamed_stmt_context = NULL;


static bool EchoQuery = false;      /* default don't echo */

/*
 * people who want to use EOF should #define DONTUSENEWLINE in
 * tcop/tcopdebug.h
 */
#ifndef TCOP_DONTUSENEWLINE
static int  UseNewLine = 1;         /* Use newlines query delimiters (the default) */
#else
static int  UseNewLine = 0;         /* Use EOF as query delimiters */
#endif   /* TCOP_DONTUSENEWLINE */


/* ----------------------------------------------------------------
 *          decls for routines only used in this file
 * ----------------------------------------------------------------
 */
static int  InteractiveBackend(StringInfo inBuf);
static int  interactive_getc(void);
static int  SocketBackend(StringInfo inBuf);
static int  ReadCommand(StringInfo inBuf);
static List *pg_rewrite_query(Query *query);
static bool check_log_statement(List *stmt_list);
static int  errdetail_execute(List *raw_parsetree_list);
static int  errdetail_params(ParamListInfo params);
static void start_xact_command(void);
static void finish_xact_command(void);
static bool IsTransactionExitStmt(Node *parsetree);
static bool IsTransactionExitStmtList(List *parseTrees);
static bool IsTransactionStmtList(List *parseTrees);
static void drop_unnamed_stmt(void);
static void SigHupHandler(SIGNAL_ARGS);
static void log_disconnections(int code, Datum arg);


/* ----------------------------------------------------------------
 *          routines to obtain user input
 * ----------------------------------------------------------------
 */

/* ----------------
 *    InteractiveBackend() is called for user interactive connections
 *
 *    the string entered by the user is placed in its parameter inBuf,
 *    and we act like a Q message was received.
 *
 *    EOF is returned if end-of-file input is seen; time to shut down.
 * ----------------
 */

static int
InteractiveBackend(StringInfo inBuf)
{
      int               c;                      /* character read from getc() */
      bool        end = false;      /* end-of-input flag */
      bool        backslashSeen = false;  /* have we seen a \ ? */

      /*
       * display a prompt and obtain input from the user
       */
      printf("backend> ");
      fflush(stdout);

      resetStringInfo(inBuf);

      if (UseNewLine)
      {
            /*
             * if we are using \n as a delimiter, then read characters until the
             * \n.
             */
            while ((c = interactive_getc()) != EOF)
            {
                  if (c == '\n')
                  {
                        if (backslashSeen)
                        {
                              /* discard backslash from inBuf */
                              inBuf->data[--inBuf->len] = '\0';
                              backslashSeen = false;
                              continue;
                        }
                        else
                        {
                              /* keep the newline character */
                              appendStringInfoChar(inBuf, '\n');
                              break;
                        }
                  }
                  else if (c == '\\')
                        backslashSeen = true;
                  else
                        backslashSeen = false;

                  appendStringInfoChar(inBuf, (char) c);
            }

            if (c == EOF)
                  end = true;
      }
      else
      {
            /*
             * otherwise read characters until EOF.
             */
            while ((c = interactive_getc()) != EOF)
                  appendStringInfoChar(inBuf, (char) c);

            /* No input before EOF signal means time to quit. */
            if (inBuf->len == 0)
                  end = true;
      }

      if (end)
            return EOF;

      /*
       * otherwise we have a user query so process it.
       */

      /* Add '\0' to make it look the same as message case. */
      appendStringInfoChar(inBuf, (char) '\0');

      /*
       * if the query echo flag was given, print the query..
       */
      if (EchoQuery)
            printf("statement: %s\n", inBuf->data);
      fflush(stdout);

      return 'Q';
}

/*
 * interactive_getc -- collect one character from stdin
 *
 * Even though we are not reading from a "client" process, we still want to
 * respond to signals, particularly SIGTERM/SIGQUIT.  Hence we must use
 * prepare_for_client_read and client_read_ended.
 */
static int
interactive_getc(void)
{
      int               c;

      prepare_for_client_read();
      c = getc(stdin);
      client_read_ended();
      return c;
}

/* ----------------
 *    SocketBackend()         Is called for frontend-backend connections
 *
 *    Returns the message type code, and loads message body data into inBuf.
 *
 *    EOF is returned if the connection is lost.
 * ----------------
 */
static int
SocketBackend(StringInfo inBuf)
{
      int               qtype;

      /*
       * Get message type code from the frontend.
       */
      qtype = pq_getbyte();

      if (qtype == EOF)             /* frontend disconnected */
      {
            ereport(COMMERROR,
                        (errcode(ERRCODE_PROTOCOL_VIOLATION),
                         errmsg("unexpected EOF on client connection")));
            return qtype;
      }

      /*
       * Validate message type code before trying to read body; if we have lost
       * sync, better to say "command unknown" than to run out of memory because
       * we used garbage as a length word.
       *
       * This also gives us a place to set the doing_extended_query_message flag
       * as soon as possible.
       */
      switch (qtype)
      {
            case 'Q':                     /* simple query */
                  doing_extended_query_message = false;
                  if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
                  {
                        /* old style without length word; convert */
                        if (pq_getstring(inBuf))
                        {
                              ereport(COMMERROR,
                                          (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                           errmsg("unexpected EOF on client connection")));
                              return EOF;
                        }
                  }
                  break;

            case 'F':                     /* fastpath function call */
                  /* we let fastpath.c cope with old-style input of this */
                  doing_extended_query_message = false;
                  break;

            case 'X':                     /* terminate */
                  doing_extended_query_message = false;
                  ignore_till_sync = false;
                  break;

            case 'B':                     /* bind */
            case 'C':                     /* close */
            case 'D':                     /* describe */
            case 'E':                     /* execute */
            case 'H':                     /* flush */
            case 'P':                     /* parse */
                  doing_extended_query_message = true;
                  /* these are only legal in protocol 3 */
                  if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
                        ereport(FATAL,
                                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                     errmsg("invalid frontend message type %d", qtype)));
                  break;

            case 'S':                     /* sync */
                  /* stop any active skip-till-Sync */
                  ignore_till_sync = false;
                  /* mark not-extended, so that a new error doesn't begin skip */
                  doing_extended_query_message = false;
                  /* only legal in protocol 3 */
                  if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
                        ereport(FATAL,
                                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                     errmsg("invalid frontend message type %d", qtype)));
                  break;

            case 'd':                     /* copy data */
            case 'c':                     /* copy done */
            case 'f':                     /* copy fail */
                  doing_extended_query_message = false;
                  /* these are only legal in protocol 3 */
                  if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
                        ereport(FATAL,
                                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                     errmsg("invalid frontend message type %d", qtype)));
                  break;

            default:

                  /*
                   * Otherwise we got garbage from the frontend.  We treat this as
                   * fatal because we have probably lost message boundary sync, and
                   * there's no good way to recover.
                   */
                  ereport(FATAL,
                              (errcode(ERRCODE_PROTOCOL_VIOLATION),
                               errmsg("invalid frontend message type %d", qtype)));
                  break;
      }

      /*
       * In protocol version 3, all frontend messages have a length word next
       * after the type code; we can read the message contents independently of
       * the type.
       */
      if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
      {
            if (pq_getmessage(inBuf, 0))
                  return EOF;             /* suitable message already logged */
      }

      return qtype;
}

/* ----------------
 *          ReadCommand reads a command from either the frontend or
 *          standard input, places it in inBuf, and returns the
 *          message type code (first byte of the message).
 *          EOF is returned if end of file.
 * ----------------
 */
static int
ReadCommand(StringInfo inBuf)
{
      int               result;

      if (whereToSendOutput == DestRemote)
            result = SocketBackend(inBuf);
      else
            result = InteractiveBackend(inBuf);
      return result;
}

/*
 * prepare_for_client_read -- set up to possibly block on client input
 *
 * This must be called immediately before any low-level read from the
 * client connection.  It is necessary to do it at a sufficiently low level
 * that there won't be any other operations except the read kernel call
 * itself between this call and the subsequent client_read_ended() call.
 * In particular there mustn't be use of malloc() or other potentially
 * non-reentrant libc functions.  This restriction makes it safe for us
 * to allow interrupt service routines to execute nontrivial code while
 * we are waiting for input.
 */
void
prepare_for_client_read(void)
{
      if (DoingCommandRead)
      {
            /* Enable immediate processing of asynchronous signals */
            EnableNotifyInterrupt();
            EnableCatchupInterrupt();

            /* Allow "die" interrupt to be processed while waiting */
            ImmediateInterruptOK = true;

            /* And don't forget to detect one that already arrived */
            QueryCancelPending = false;
            CHECK_FOR_INTERRUPTS();
      }
}

/*
 * client_read_ended -- get out of the client-input state
 */
void
client_read_ended(void)
{
      if (DoingCommandRead)
      {
            ImmediateInterruptOK = false;
            QueryCancelPending = false;         /* forget any CANCEL signal */

            DisableNotifyInterrupt();
            DisableCatchupInterrupt();
      }
}


/*
 * Parse a query string and pass it through the rewriter.
 *
 * A list of Query nodes is returned, since the string might contain
 * multiple queries and/or the rewriter might expand one query to several.
 *
 * NOTE: this routine is no longer used for processing interactive queries,
 * but it is still needed for parsing of SQL function bodies.
 */
List *
pg_parse_and_rewrite(const char *query_string,  /* string to execute */
                               Oid *paramTypes, /* parameter types */
                               int numParams)         /* number of parameters */
{
      List     *raw_parsetree_list;
      List     *querytree_list;
      ListCell   *list_item;

      /*
       * (1) parse the request string into a list of raw parse trees.
       */
      raw_parsetree_list = pg_parse_query(query_string);

      /*
       * (2) Do parse analysis and rule rewrite.
       */
      querytree_list = NIL;
      foreach(list_item, raw_parsetree_list)
      {
            Node     *parsetree = (Node *) lfirst(list_item);

            querytree_list = list_concat(querytree_list,
                                                       pg_analyze_and_rewrite(parsetree,
                                                                                          query_string,
                                                                                          paramTypes,
                                                                                          numParams));
      }

      return querytree_list;
}

/*
 * Do raw parsing (only).
 *
 * A list of parsetrees is returned, since there might be multiple
 * commands in the given string.
 *
 * NOTE: for interactive queries, it is important to keep this routine
 * separate from the analysis & rewrite stages.  Analysis and rewriting
 * cannot be done in an aborted transaction, since they require access to
 * database tables.  So, we rely on the raw parser to determine whether
 * we've seen a COMMIT or ABORT command; when we are in abort state, other
 * commands are not processed any further than the raw parse stage.
 */
List *
pg_parse_query(const char *query_string)
{
      List     *raw_parsetree_list;

      TRACE_POSTGRESQL_QUERY_PARSE_START(query_string);

      if (log_parser_stats)
            ResetUsage();

      raw_parsetree_list = raw_parser(query_string);

      if (log_parser_stats)
            ShowUsage("PARSER STATISTICS");

#ifdef COPY_PARSE_PLAN_TREES
      /* Optional debugging check: pass raw parsetrees through copyObject() */
      {
            List     *new_list = (List *) copyObject(raw_parsetree_list);

            /* This checks both copyObject() and the equal() routines... */
            if (!equal(new_list, raw_parsetree_list))
                  elog(WARNING, "copyObject() failed to produce an equal raw parse tree");
            else
                  raw_parsetree_list = new_list;
      }
#endif

      TRACE_POSTGRESQL_QUERY_PARSE_DONE(query_string);

      return raw_parsetree_list;
}

/*
 * Given a raw parsetree (gram.y output), and optionally information about
 * types of parameter symbols ($n), perform parse analysis and rule rewriting.
 *
 * A list of Query nodes is returned, since either the analyzer or the
 * rewriter might expand one query to several.
 *
 * NOTE: for reasons mentioned above, this must be separate from raw parsing.
 */
List *
pg_analyze_and_rewrite(Node *parsetree, const char *query_string,
                                 Oid *paramTypes, int numParams)
{
      Query    *query;
      List     *querytree_list;

      TRACE_POSTGRESQL_QUERY_REWRITE_START(query_string);

      /*
       * (1) Perform parse analysis.
       */
      if (log_parser_stats)
            ResetUsage();

      query = parse_analyze(parsetree, query_string, paramTypes, numParams);

      if (log_parser_stats)
            ShowUsage("PARSE ANALYSIS STATISTICS");

      /*
       * (2) Rewrite the queries, as necessary
       */
      querytree_list = pg_rewrite_query(query);

      TRACE_POSTGRESQL_QUERY_REWRITE_DONE(query_string);

      return querytree_list;
}

/*
 * Perform rewriting of a query produced by parse analysis.
 *
 * Note: query must just have come from the parser, because we do not do
 * AcquireRewriteLocks() on it.
 */
static List *
pg_rewrite_query(Query *query)
{
      List     *querytree_list;

      if (Debug_print_parse)
            elog_node_display(LOG, "parse tree", query,
                                      Debug_pretty_print);

      if (log_parser_stats)
            ResetUsage();

      if (query->commandType == CMD_UTILITY)
      {
            /* don't rewrite utilities, just dump 'em into result list */
            querytree_list = list_make1(query);
      }
      else
      {
            /* rewrite regular queries */
            querytree_list = QueryRewrite(query);
      }

      if (log_parser_stats)
            ShowUsage("REWRITER STATISTICS");

#ifdef COPY_PARSE_PLAN_TREES
      /* Optional debugging check: pass querytree output through copyObject() */
      {
            List     *new_list;

            new_list = (List *) copyObject(querytree_list);
            /* This checks both copyObject() and the equal() routines... */
            if (!equal(new_list, querytree_list))
                  elog(WARNING, "copyObject() failed to produce equal parse tree");
            else
                  querytree_list = new_list;
      }
#endif

      if (Debug_print_rewritten)
            elog_node_display(LOG, "rewritten parse tree", querytree_list,
                                      Debug_pretty_print);

      return querytree_list;
}


/*
 * Generate a plan for a single already-rewritten query.
 * This is a thin wrapper around planner() and takes the same parameters.
 */
PlannedStmt *
pg_plan_query(Query *querytree, int cursorOptions, ParamListInfo boundParams)
{
      PlannedStmt *plan;

      /* Utility commands have no plans. */
      if (querytree->commandType == CMD_UTILITY)
            return NULL;

      /* Planner must have a snapshot in case it calls user-defined functions. */
      Assert(ActiveSnapshotSet());

      TRACE_POSTGRESQL_QUERY_PLAN_START();

      if (log_planner_stats)
            ResetUsage();

      /* call the optimizer */
      plan = planner(querytree, cursorOptions, boundParams);

      if (log_planner_stats)
            ShowUsage("PLANNER STATISTICS");

#ifdef COPY_PARSE_PLAN_TREES
      /* Optional debugging check: pass plan output through copyObject() */
      {
            PlannedStmt *new_plan = (PlannedStmt *) copyObject(plan);

            /*
             * equal() currently does not have routines to compare Plan nodes, so
             * don't try to test equality here.  Perhaps fix someday?
             */
#ifdef NOT_USED
            /* This checks both copyObject() and the equal() routines... */
            if (!equal(new_plan, plan))
                  elog(WARNING, "copyObject() failed to produce an equal plan tree");
            else
#endif
                  plan = new_plan;
      }
#endif

      /*
       * Print plan if debugging.
       */
      if (Debug_print_plan)
            elog_node_display(LOG, "plan", plan, Debug_pretty_print);

      TRACE_POSTGRESQL_QUERY_PLAN_DONE();

      return plan;
}

/*
 * Generate plans for a list of already-rewritten queries.
 *
 * Normal optimizable statements generate PlannedStmt entries in the result
 * list.  Utility statements are simply represented by their statement nodes.
 */
List *
pg_plan_queries(List *querytrees, int cursorOptions, ParamListInfo boundParams)
{
      List     *stmt_list = NIL;
      ListCell   *query_list;

      foreach(query_list, querytrees)
      {
            Query    *query = (Query *) lfirst(query_list);
            Node     *stmt;

            if (query->commandType == CMD_UTILITY)
            {
                  /* Utility commands have no plans. */
                  stmt = query->utilityStmt;
            }
            else
            {
                  stmt = (Node *) pg_plan_query(query, cursorOptions, boundParams);
            }

            stmt_list = lappend(stmt_list, stmt);
      }

      return stmt_list;
}


/*
 * exec_simple_query
 *
 * Execute a "simple Query" protocol message.
 */
static void
exec_simple_query(const char *query_string)
{
      CommandDest dest = whereToSendOutput;
      MemoryContext oldcontext;
      List     *parsetree_list;
      ListCell   *parsetree_item;
      bool        save_log_statement_stats = log_statement_stats;
      bool        was_logged = false;
      bool        isTopLevel;
      char        msec_str[32];


      /*
       * Report query to various monitoring facilities.
       */
      debug_query_string = query_string;

      pgstat_report_activity(query_string);

      TRACE_POSTGRESQL_QUERY_START(query_string);

      /*
       * We use save_log_statement_stats so ShowUsage doesn't report incorrect
       * results because ResetUsage wasn't called.
       */
      if (save_log_statement_stats)
            ResetUsage();

      /*
       * Start up a transaction command.  All queries generated by the
       * query_string will be in this same command block, *unless* we find a
       * BEGIN/COMMIT/ABORT statement; we have to force a new xact command after
       * one of those, else bad things will happen in xact.c. (Note that this
       * will normally change current memory context.)
       */
      start_xact_command();

      /*
       * Zap any pre-existing unnamed statement.      (While not strictly necessary,
       * it seems best to define simple-Query mode as if it used the unnamed
       * statement and portal; this ensures we recover any storage used by prior
       * unnamed operations.)
       */
      drop_unnamed_stmt();

      /*
       * Switch to appropriate context for constructing parsetrees.
       */
      oldcontext = MemoryContextSwitchTo(MessageContext);

      /*
       * Do basic parsing of the query or queries (this should be safe even if
       * we are in aborted transaction state!)
       */
      parsetree_list = pg_parse_query(query_string);

      /* Log immediately if dictated by log_statement */
      if (check_log_statement(parsetree_list))
      {
            ereport(LOG,
                        (errmsg("statement: %s", query_string),
                         errhidestmt(true),
                         errdetail_execute(parsetree_list)));
            was_logged = true;
      }

      /*
       * Switch back to transaction context to enter the loop.
       */
      MemoryContextSwitchTo(oldcontext);

      /*
       * We'll tell PortalRun it's a top-level command iff there's exactly one
       * raw parsetree.  If more than one, it's effectively a transaction block
       * and we want PreventTransactionChain to reject unsafe commands. (Note:
       * we're assuming that query rewrite cannot add commands that are
       * significant to PreventTransactionChain.)
       */
      isTopLevel = (list_length(parsetree_list) == 1);

      /*
       * Run through the raw parsetree(s) and process each one.
       */
      foreach(parsetree_item, parsetree_list)
      {
            Node     *parsetree = (Node *) lfirst(parsetree_item);
            bool        snapshot_set = false;
            const char *commandTag;
            char        completionTag[COMPLETION_TAG_BUFSIZE];
            List     *querytree_list,
                           *plantree_list;
            Portal            portal;
            DestReceiver *receiver;
            int16       format;

            /*
             * Get the command name for use in status display (it also becomes the
             * default completion tag, down inside PortalRun).    Set ps_status and
             * do any special start-of-SQL-command processing needed by the
             * destination.
             */
            commandTag = CreateCommandTag(parsetree);

            set_ps_display(commandTag, false);

            BeginCommand(commandTag, dest);

            /*
             * If we are in an aborted transaction, reject all commands except
             * COMMIT/ABORT.  It is important that this test occur before we try
             * to do parse analysis, rewrite, or planning, since all those phases
             * try to do database accesses, which may fail in abort state. (It
             * might be safe to allow some additional utility commands in this
             * state, but not many...)
             */
            if (IsAbortedTransactionBlockState() &&
                  !IsTransactionExitStmt(parsetree))
                  ereport(ERROR,
                              (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                               errmsg("current transaction is aborted, "
                                    "commands ignored until end of transaction block")));

            /* Make sure we are in a transaction command */
            start_xact_command();

            /* If we got a cancel signal in parsing or prior command, quit */
            CHECK_FOR_INTERRUPTS();

            /*
             * Set up a snapshot if parse analysis/planning will need one.
             */
            if (analyze_requires_snapshot(parsetree))
            {
                  PushActiveSnapshot(GetTransactionSnapshot());
                  snapshot_set = true;
            }

            /*
             * OK to analyze, rewrite, and plan this query.
             *
             * Switch to appropriate context for constructing querytrees (again,
             * these must outlive the execution context).
             */
            oldcontext = MemoryContextSwitchTo(MessageContext);

            querytree_list = pg_analyze_and_rewrite(parsetree, query_string,
                                                                        NULL, 0);

            plantree_list = pg_plan_queries(querytree_list, 0, NULL);

            /* Done with the snapshot used for parsing/planning */
            if (snapshot_set)
                  PopActiveSnapshot();

            /* If we got a cancel signal in analysis or planning, quit */
            CHECK_FOR_INTERRUPTS();

            /*
             * Create unnamed portal to run the query or queries in. If there
             * already is one, silently drop it.
             */
            portal = CreatePortal("", true, true);
            /* Don't display the portal in pg_cursors */
            portal->visible = false;

            /*
             * We don't have to copy anything into the portal, because everything
             * we are passing here is in MessageContext, which will outlive the
             * portal anyway.
             */
            PortalDefineQuery(portal,
                                      NULL,
                                      query_string,
                                      commandTag,
                                      plantree_list,
                                      NULL);

            /*
             * Start the portal.  No parameters here.
             */
            PortalStart(portal, NULL, InvalidSnapshot);

            /*
             * Select the appropriate output format: text unless we are doing a
             * FETCH from a binary cursor.      (Pretty grotty to have to do this here
             * --- but it avoids grottiness in other places.  Ah, the joys of
             * backward compatibility...)
             */
            format = 0;                   /* TEXT is default */
            if (IsA(parsetree, FetchStmt))
            {
                  FetchStmt  *stmt = (FetchStmt *) parsetree;

                  if (!stmt->ismove)
                  {
                        Portal            fportal = GetPortalByName(stmt->portalname);

                        if (PortalIsValid(fportal) &&
                              (fportal->cursorOptions & CURSOR_OPT_BINARY))
                              format = 1; /* BINARY */
                  }
            }
            PortalSetResultFormat(portal, 1, &format);

            /*
             * Now we can create the destination receiver object.
             */
            receiver = CreateDestReceiver(dest);
            if (dest == DestRemote)
                  SetRemoteDestReceiverParams(receiver, portal);

            /*
             * Switch back to transaction context for execution.
             */
            MemoryContextSwitchTo(oldcontext);

            /*
             * Run the portal to completion, and then drop it (and the receiver).
             */
            (void) PortalRun(portal,
                                     FETCH_ALL,
                                     isTopLevel,
                                     receiver,
                                     receiver,
                                     completionTag);

            (*receiver->rDestroy) (receiver);

            PortalDrop(portal, false);

            if (IsA(parsetree, TransactionStmt))
            {
                  /*
                   * If this was a transaction control statement, commit it. We will
                   * start a new xact command for the next command (if any).
                   */
                  finish_xact_command();
            }
            else if (lnext(parsetree_item) == NULL)
            {
                  /*
                   * If this is the last parsetree of the query string, close down
                   * transaction statement before reporting command-complete.  This
                   * is so that any end-of-transaction errors are reported before
                   * the command-complete message is issued, to avoid confusing
                   * clients who will expect either a command-complete message or an
                   * error, not one and then the other.  But for compatibility with
                   * historical Postgres behavior, we do not force a transaction
                   * boundary between queries appearing in a single query string.
                   */
                  finish_xact_command();
            }
            else
            {
                  /*
                   * We need a CommandCounterIncrement after every query, except
                   * those that start or end a transaction block.
                   */
                  CommandCounterIncrement();
            }

            /*
             * Tell client that we're done with this query.  Note we emit exactly
             * one EndCommand report for each raw parsetree, thus one for each SQL
             * command the client sent, regardless of rewriting. (But a command
             * aborted by error will not send an EndCommand report at all.)
             */
            EndCommand(completionTag, dest);
      }                                         /* end loop over parsetrees */

      /*
       * Close down transaction statement, if one is open.
       */
      finish_xact_command();

      /*
       * If there were no parsetrees, return EmptyQueryResponse message.
       */
      if (!parsetree_list)
            NullCommand(dest);

      /*
       * Emit duration logging if appropriate.
       */
      switch (check_log_duration(msec_str, was_logged))
      {
            case 1:
                  ereport(LOG,
                              (errmsg("duration: %s ms", msec_str),
                               errhidestmt(true)));
                  break;
            case 2:
                  ereport(LOG,
                              (errmsg("duration: %s ms  statement: %s",
                                          msec_str, query_string),
                               errhidestmt(true),
                               errdetail_execute(parsetree_list)));
                  break;
      }

      if (save_log_statement_stats)
            ShowUsage("QUERY STATISTICS");

      TRACE_POSTGRESQL_QUERY_DONE(query_string);

      debug_query_string = NULL;
}

/*
 * exec_parse_message
 *
 * Execute a "Parse" protocol message.
 */
static void
exec_parse_message(const char *query_string,    /* string to execute */
                           const char *stmt_name,           /* name for prepared stmt */
                           Oid *paramTypes,           /* parameter types */
                           int numParams)       /* number of parameters */
{
      MemoryContext oldcontext;
      List     *parsetree_list;
      Node     *raw_parse_tree;
      const char *commandTag;
      List     *querytree_list,
                     *stmt_list;
      bool        is_named;
      bool        fully_planned;
      bool        save_log_statement_stats = log_statement_stats;
      char        msec_str[32];

      /*
       * Report query to various monitoring facilities.
       */
      debug_query_string = query_string;

      pgstat_report_activity(query_string);

      set_ps_display("PARSE", false);

      if (save_log_statement_stats)
            ResetUsage();

      ereport(DEBUG2,
                  (errmsg("parse %s: %s",
                              *stmt_name ? stmt_name : "<unnamed>",
                              query_string)));

      /*
       * Start up a transaction command so we can run parse analysis etc. (Note
       * that this will normally change current memory context.) Nothing happens
       * if we are already in one.
       */
      start_xact_command();

      /*
       * Switch to appropriate context for constructing parsetrees.
       *
       * We have two strategies depending on whether the prepared statement is
       * named or not.  For a named prepared statement, we do parsing in
       * MessageContext and copy the finished trees into the prepared
       * statement's plancache entry; then the reset of MessageContext releases
       * temporary space used by parsing and planning.  For an unnamed prepared
       * statement, we assume the statement isn't going to hang around long, so
       * getting rid of temp space quickly is probably not worth the costs of
       * copying parse/plan trees.  So in this case, we create the plancache
       * entry's context here, and do all the parsing work therein.
       */
      is_named = (stmt_name[0] != '\0');
      if (is_named)
      {
            /* Named prepared statement --- parse in MessageContext */
            oldcontext = MemoryContextSwitchTo(MessageContext);
      }
      else
      {
            /* Unnamed prepared statement --- release any prior unnamed stmt */
            drop_unnamed_stmt();
            /* Create context for parsing/planning */
            unnamed_stmt_context =
                  AllocSetContextCreate(CacheMemoryContext,
                                                  "unnamed prepared statement",
                                                  ALLOCSET_DEFAULT_MINSIZE,
                                                  ALLOCSET_DEFAULT_INITSIZE,
                                                  ALLOCSET_DEFAULT_MAXSIZE);
            oldcontext = MemoryContextSwitchTo(unnamed_stmt_context);
      }

      /*
       * Do basic parsing of the query or queries (this should be safe even if
       * we are in aborted transaction state!)
       */
      parsetree_list = pg_parse_query(query_string);

      /*
       * We only allow a single user statement in a prepared statement. This is
       * mainly to keep the protocol simple --- otherwise we'd need to worry
       * about multiple result tupdescs and things like that.
       */
      if (list_length(parsetree_list) > 1)
            ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
            errmsg("cannot insert multiple commands into a prepared statement")));

      if (parsetree_list != NIL)
      {
            Query    *query;
            bool        snapshot_set = false;
            int               i;

            raw_parse_tree = (Node *) linitial(parsetree_list);

            /*
             * Get the command name for possible use in status display.
             */
            commandTag = CreateCommandTag(raw_parse_tree);

            /*
             * If we are in an aborted transaction, reject all commands except
             * COMMIT/ROLLBACK.  It is important that this test occur before we
             * try to do parse analysis, rewrite, or planning, since all those
             * phases try to do database accesses, which may fail in abort state.
             * (It might be safe to allow some additional utility commands in this
             * state, but not many...)
             */
            if (IsAbortedTransactionBlockState() &&
                  !IsTransactionExitStmt(raw_parse_tree))
                  ereport(ERROR,
                              (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                               errmsg("current transaction is aborted, "
                                    "commands ignored until end of transaction block")));

            /*
             * Set up a snapshot if parse analysis/planning will need one.
             */
            if (analyze_requires_snapshot(raw_parse_tree))
            {
                  PushActiveSnapshot(GetTransactionSnapshot());
                  snapshot_set = true;
            }

            /*
             * OK to analyze, rewrite, and plan this query.  Note that the
             * originally specified parameter set is not required to be complete,
             * so we have to use parse_analyze_varparams().
             *
             * XXX must use copyObject here since parse analysis scribbles on its
             * input, and we need the unmodified raw parse tree for possible
             * replanning later.
             */
            if (log_parser_stats)
                  ResetUsage();

            query = parse_analyze_varparams(copyObject(raw_parse_tree),
                                                            query_string,
                                                            &paramTypes,
                                                            &numParams);

            /*
             * Check all parameter types got determined.
             */
            for (i = 0; i < numParams; i++)
            {
                  Oid               ptype = paramTypes[i];

                  if (ptype == InvalidOid || ptype == UNKNOWNOID)
                        ereport(ERROR,
                                    (errcode(ERRCODE_INDETERMINATE_DATATYPE),
                               errmsg("could not determine data type of parameter $%d",
                                          i + 1)));
            }

            if (log_parser_stats)
                  ShowUsage("PARSE ANALYSIS STATISTICS");

            querytree_list = pg_rewrite_query(query);

            /*
             * If this is the unnamed statement and it has parameters, defer query
             * planning until Bind.  Otherwise do it now.
             */
            if (!is_named && numParams > 0)
            {
                  stmt_list = querytree_list;
                  fully_planned = false;
            }
            else
            {
                  stmt_list = pg_plan_queries(querytree_list, 0, NULL);
                  fully_planned = true;
            }

            /* Done with the snapshot used for parsing/planning */
            if (snapshot_set)
                  PopActiveSnapshot();
      }
      else
      {
            /* Empty input string.  This is legal. */
            raw_parse_tree = NULL;
            commandTag = NULL;
            stmt_list = NIL;
            fully_planned = true;
      }

      /* If we got a cancel signal in analysis or planning, quit */
      CHECK_FOR_INTERRUPTS();

      /*
       * Store the query as a prepared statement.  See above comments.
       */
      if (is_named)
      {
            StorePreparedStatement(stmt_name,
                                             raw_parse_tree,
                                             query_string,
                                             commandTag,
                                             paramTypes,
                                             numParams,
                                             0,       /* default cursor options */
                                             stmt_list,
                                             false);
      }
      else
      {
            /*
             * paramTypes and query_string need to be copied into
             * unnamed_stmt_context.  The rest is there already
             */
            Oid            *newParamTypes;

            if (numParams > 0)
            {
                  newParamTypes = (Oid *) palloc(numParams * sizeof(Oid));
                  memcpy(newParamTypes, paramTypes, numParams * sizeof(Oid));
            }
            else
                  newParamTypes = NULL;

            unnamed_stmt_psrc = FastCreateCachedPlan(raw_parse_tree,
                                                                         pstrdup(query_string),
                                                                         commandTag,
                                                                         newParamTypes,
                                                                         numParams,
                                                                         0,         /* cursor options */
                                                                         stmt_list,
                                                                         fully_planned,
                                                                         true,
                                                                         unnamed_stmt_context);
            /* context now belongs to the plancache entry */
            unnamed_stmt_context = NULL;
      }

      MemoryContextSwitchTo(oldcontext);

      /*
       * We do NOT close the open transaction command here; that only happens
       * when the client sends Sync.      Instead, do CommandCounterIncrement just
       * in case something happened during parse/plan.
       */
      CommandCounterIncrement();

      /*
       * Send ParseComplete.
       */
      if (whereToSendOutput == DestRemote)
            pq_putemptymessage('1');

      /*
       * Emit duration logging if appropriate.
       */
      switch (check_log_duration(msec_str, false))
      {
            case 1:
                  ereport(LOG,
                              (errmsg("duration: %s ms", msec_str),
                               errhidestmt(true)));
                  break;
            case 2:
                  ereport(LOG,
                              (errmsg("duration: %s ms  parse %s: %s",
                                          msec_str,
                                          *stmt_name ? stmt_name : "<unnamed>",
                                          query_string),
                               errhidestmt(true)));
                  break;
      }

      if (save_log_statement_stats)
            ShowUsage("PARSE MESSAGE STATISTICS");

      debug_query_string = NULL;
}

/*
 * exec_bind_message
 *
 * Process a "Bind" message to create a portal from a prepared statement
 */
static void
exec_bind_message(StringInfo input_message)
{
      const char *portal_name;
      const char *stmt_name;
      int               numPFormats;
      int16    *pformats = NULL;
      int               numParams;
      int               numRFormats;
      int16    *rformats = NULL;
      CachedPlanSource *psrc;
      CachedPlan *cplan;
      Portal            portal;
      char     *query_string;
      char     *saved_stmt_name;
      ParamListInfo params;
      List     *plan_list;
      MemoryContext oldContext;
      bool        save_log_statement_stats = log_statement_stats;
      bool        snapshot_set = false;
      char        msec_str[32];

      /* Get the fixed part of the message */
      portal_name = pq_getmsgstring(input_message);
      stmt_name = pq_getmsgstring(input_message);

      ereport(DEBUG2,
                  (errmsg("bind %s to %s",
                              *portal_name ? portal_name : "<unnamed>",
                              *stmt_name ? stmt_name : "<unnamed>")));

      /* Find prepared statement */
      if (stmt_name[0] != '\0')
      {
            PreparedStatement *pstmt;

            pstmt = FetchPreparedStatement(stmt_name, true);
            psrc = pstmt->plansource;
      }
      else
      {
            /* special-case the unnamed statement */
            psrc = unnamed_stmt_psrc;
            if (!psrc)
                  ereport(ERROR,
                              (errcode(ERRCODE_UNDEFINED_PSTATEMENT),
                               errmsg("unnamed prepared statement does not exist")));
      }

      /*
       * Report query to various monitoring facilities.
       */
      debug_query_string = psrc->query_string;

      pgstat_report_activity(psrc->query_string);

      set_ps_display("BIND", false);

      if (save_log_statement_stats)
            ResetUsage();

      /*
       * Start up a transaction command so we can call functions etc. (Note that
       * this will normally change current memory context.) Nothing happens if
       * we are already in one.
       */
      start_xact_command();

      /* Switch back to message context */
      MemoryContextSwitchTo(MessageContext);

      /* Get the parameter format codes */
      numPFormats = pq_getmsgint(input_message, 2);
      if (numPFormats > 0)
      {
            int               i;

            pformats = (int16 *) palloc(numPFormats * sizeof(int16));
            for (i = 0; i < numPFormats; i++)
                  pformats[i] = pq_getmsgint(input_message, 2);
      }

      /* Get the parameter value count */
      numParams = pq_getmsgint(input_message, 2);

      if (numPFormats > 1 && numPFormats != numParams)
            ereport(ERROR,
                        (errcode(ERRCODE_PROTOCOL_VIOLATION),
                  errmsg("bind message has %d parameter formats but %d parameters",
                           numPFormats, numParams)));

      if (numParams != psrc->num_params)
            ereport(ERROR,
                        (errcode(ERRCODE_PROTOCOL_VIOLATION),
                         errmsg("bind message supplies %d parameters, but prepared statement \"%s\" requires %d",
                                    numParams, stmt_name, psrc->num_params)));

      /*
       * If we are in aborted transaction state, the only portals we can
       * actually run are those containing COMMIT or ROLLBACK commands. We
       * disallow binding anything else to avoid problems with infrastructure
       * that expects to run inside a valid transaction.    We also disallow
       * binding any parameters, since we can't risk calling user-defined I/O
       * functions.
       */
      if (IsAbortedTransactionBlockState() &&
            (!IsTransactionExitStmt(psrc->raw_parse_tree) ||
             numParams != 0))
            ereport(ERROR,
                        (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                         errmsg("current transaction is aborted, "
                                    "commands ignored until end of transaction block")));

      /*
       * Create the portal.  Allow silent replacement of an existing portal only
       * if the unnamed portal is specified.
       */
      if (portal_name[0] == '\0')
            portal = CreatePortal(portal_name, true, true);
      else
            portal = CreatePortal(portal_name, false, false);

      /*
       * Prepare to copy stuff into the portal's memory context.  We do all this
       * copying first, because it could possibly fail (out-of-memory) and we
       * don't want a failure to occur between RevalidateCachedPlan and
       * PortalDefineQuery; that would result in leaking our plancache refcount.
       */
      oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));

      /* Copy the plan's query string into the portal */
      query_string = pstrdup(psrc->query_string);

      /* Likewise make a copy of the statement name, unless it's unnamed */
      if (stmt_name[0])
            saved_stmt_name = pstrdup(stmt_name);
      else
            saved_stmt_name = NULL;

      /*
       * Set a snapshot if we have parameters to fetch (since the input
       * functions might need it) or the query isn't a utility command (and
       * hence could require redoing parse analysis and planning).
       */
      if (numParams > 0 || analyze_requires_snapshot(psrc->raw_parse_tree))
      {
            PushActiveSnapshot(GetTransactionSnapshot());
            snapshot_set = true;
      }

      /*
       * Fetch parameters, if any, and store in the portal's memory context.
       */
      if (numParams > 0)
      {
            int               paramno;

            /* sizeof(ParamListInfoData) includes the first array element */
            params = (ParamListInfo) palloc(sizeof(ParamListInfoData) +
                                                   (numParams - 1) *sizeof(ParamExternData));
            params->numParams = numParams;

            for (paramno = 0; paramno < numParams; paramno++)
            {
                  Oid               ptype = psrc->param_types[paramno];
                  int32       plength;
                  Datum       pval;
                  bool        isNull;
                  StringInfoData pbuf;
                  char        csave;
                  int16       pformat;

                  plength = pq_getmsgint(input_message, 4);
                  isNull = (plength == -1);

                  if (!isNull)
                  {
                        const char *pvalue = pq_getmsgbytes(input_message, plength);

                        /*
                         * Rather than copying data around, we just set up a phony
                         * StringInfo pointing to the correct portion of the message
                         * buffer.  We assume we can scribble on the message buffer so
                         * as to maintain the convention that StringInfos have a
                         * trailing null.  This is grotty but is a big win when
                         * dealing with very large parameter strings.
                         */
                        pbuf.data = (char *) pvalue;
                        pbuf.maxlen = plength + 1;
                        pbuf.len = plength;
                        pbuf.cursor = 0;

                        csave = pbuf.data[plength];
                        pbuf.data[plength] = '\0';
                  }
                  else
                  {
                        pbuf.data = NULL;       /* keep compiler quiet */
                        csave = 0;
                  }

                  if (numPFormats > 1)
                        pformat = pformats[paramno];
                  else if (numPFormats > 0)
                        pformat = pformats[0];
                  else
                        pformat = 0;      /* default = text */

                  if (pformat == 0) /* text mode */
                  {
                        Oid               typinput;
                        Oid               typioparam;
                        char     *pstring;

                        getTypeInputInfo(ptype, &typinput, &typioparam);

                        /*
                         * We have to do encoding conversion before calling the
                         * typinput routine.
                         */
                        if (isNull)
                              pstring = NULL;
                        else
                              pstring = pg_client_to_server(pbuf.data, plength);

                        pval = OidInputFunctionCall(typinput, pstring, typioparam, -1);

                        /* Free result of encoding conversion, if any */
                        if (pstring && pstring != pbuf.data)
                              pfree(pstring);
                  }
                  else if (pformat == 1)        /* binary mode */
                  {
                        Oid               typreceive;
                        Oid               typioparam;
                        StringInfo  bufptr;

                        /*
                         * Call the parameter type's binary input converter
                         */
                        getTypeBinaryInputInfo(ptype, &typreceive, &typioparam);

                        if (isNull)
                              bufptr = NULL;
                        else
                              bufptr = &pbuf;

                        pval = OidReceiveFunctionCall(typreceive, bufptr, typioparam, -1);

                        /* Trouble if it didn't eat the whole buffer */
                        if (!isNull && pbuf.cursor != pbuf.len)
                              ereport(ERROR,
                                          (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
                                           errmsg("incorrect binary data format in bind parameter %d",
                                                      paramno + 1)));
                  }
                  else
                  {
                        ereport(ERROR,
                                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                     errmsg("unsupported format code: %d",
                                                pformat)));
                        pval = 0;         /* keep compiler quiet */
                  }

                  /* Restore message buffer contents */
                  if (!isNull)
                        pbuf.data[plength] = csave;

                  params->params[paramno].value = pval;
                  params->params[paramno].isnull = isNull;

                  /*
                   * We mark the params as CONST.  This has no effect if we already
                   * did planning, but if we didn't, it licenses the planner to
                   * substitute the parameters directly into the one-shot plan we
                   * will generate below.
                   */
                  params->params[paramno].pflags = PARAM_FLAG_CONST;
                  params->params[paramno].ptype = ptype;
            }
      }
      else
            params = NULL;

      /* Done storing stuff in portal's context */
      MemoryContextSwitchTo(oldContext);

      /* Get the result format codes */
      numRFormats = pq_getmsgint(input_message, 2);
      if (numRFormats > 0)
      {
            int               i;

            rformats = (int16 *) palloc(numRFormats * sizeof(int16));
            for (i = 0; i < numRFormats; i++)
                  rformats[i] = pq_getmsgint(input_message, 2);
      }

      pq_getmsgend(input_message);

      if (psrc->fully_planned)
      {
            /*
             * Revalidate the cached plan; this may result in replanning.  Any
             * cruft will be generated in MessageContext.  The plan refcount will
             * be assigned to the Portal, so it will be released at portal
             * destruction.
             */
            cplan = RevalidateCachedPlan(psrc, false);
            plan_list = cplan->stmt_list;
      }
      else
      {
            List     *query_list;

            /*
             * Revalidate the cached plan; this may result in redoing parse
             * analysis and rewriting (but not planning).  Any cruft will be
             * generated in MessageContext.  The plan refcount is assigned to
             * CurrentResourceOwner.
             */
            cplan = RevalidateCachedPlan(psrc, true);

            /*
             * We didn't plan the query before, so do it now.  This allows the
             * planner to make use of the concrete parameter values we now have.
             * Because we use PARAM_FLAG_CONST, the plan is good only for this set
             * of param values, and so we generate the plan in the portal's own
             * memory context where it will be thrown away after use. As in
             * exec_parse_message, we make no attempt to recover planner temporary
             * memory until the end of the operation.
             *
             * XXX because the planner has a bad habit of scribbling on its input,
             * we have to make a copy of the parse trees.  FIXME someday.
             */
            oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
            query_list = copyObject(cplan->stmt_list);
            plan_list = pg_plan_queries(query_list, 0, params);
            MemoryContextSwitchTo(oldContext);

            /* We no longer need the cached plan refcount ... */
            ReleaseCachedPlan(cplan, true);
            /* ... and we don't want the portal to depend on it, either */
            cplan = NULL;
      }

      /*
       * Now we can define the portal.
       *
       * DO NOT put any code that could possibly throw an error between the
       * above "RevalidateCachedPlan(psrc, false)" call and here.
       */
      PortalDefineQuery(portal,
                                saved_stmt_name,
                                query_string,
                                psrc->commandTag,
                                plan_list,
                                cplan);

      /* Done with the snapshot used for parameter I/O and parsing/planning */
      if (snapshot_set)
            PopActiveSnapshot();

      /*
       * And we're ready to start portal execution.
       */
      PortalStart(portal, params, InvalidSnapshot);

      /*
       * Apply the result format requests to the portal.
       */
      PortalSetResultFormat(portal, numRFormats, rformats);

      /*
       * Send BindComplete.
       */
      if (whereToSendOutput == DestRemote)
            pq_putemptymessage('2');

      /*
       * Emit duration logging if appropriate.
       */
      switch (check_log_duration(msec_str, false))
      {
            case 1:
                  ereport(LOG,
                              (errmsg("duration: %s ms", msec_str),
                               errhidestmt(true)));
                  break;
            case 2:
                  ereport(LOG,
                              (errmsg("duration: %s ms  bind %s%s%s: %s",
                                          msec_str,
                                          *stmt_name ? stmt_name : "<unnamed>",
                                          *portal_name ? "/" : "",
                                          *portal_name ? portal_name : "",
                                          psrc->query_string),
                               errhidestmt(true),
                               errdetail_params(params)));
                  break;
      }

      if (save_log_statement_stats)
            ShowUsage("BIND MESSAGE STATISTICS");

      debug_query_string = NULL;
}

/*
 * exec_execute_message
 *
 * Process an "Execute" message for a portal
 */
static void
exec_execute_message(const char *portal_name, long max_rows)
{
      CommandDest dest;
      DestReceiver *receiver;
      Portal            portal;
      bool        completed;
      char        completionTag[COMPLETION_TAG_BUFSIZE];
      const char *sourceText;
      const char *prepStmtName;
      ParamListInfo portalParams;
      bool        save_log_statement_stats = log_statement_stats;
      bool        is_xact_command;
      bool        execute_is_fetch;
      bool        was_logged = false;
      char        msec_str[32];

      /* Adjust destination to tell printtup.c what to do */
      dest = whereToSendOutput;
      if (dest == DestRemote)
            dest = DestRemoteExecute;

      portal = GetPortalByName(portal_name);
      if (!PortalIsValid(portal))
            ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_CURSOR),
                         errmsg("portal \"%s\" does not exist", portal_name)));

      /*
       * If the original query was a null string, just return
       * EmptyQueryResponse.
       */
      if (portal->commandTag == NULL)
      {
            Assert(portal->stmts == NIL);
            NullCommand(dest);
            return;
      }

      /* Does the portal contain a transaction command? */
      is_xact_command = IsTransactionStmtList(portal->stmts);

      /*
       * We must copy the sourceText and prepStmtName into MessageContext in
       * case the portal is destroyed during finish_xact_command. Can avoid the
       * copy if it's not an xact command, though.
       */
      if (is_xact_command)
      {
            sourceText = pstrdup(portal->sourceText);
            if (portal->prepStmtName)
                  prepStmtName = pstrdup(portal->prepStmtName);
            else
                  prepStmtName = "<unnamed>";

            /*
             * An xact command shouldn't have any parameters, which is a good
             * thing because they wouldn't be around after finish_xact_command.
             */
            portalParams = NULL;
      }
      else
      {
            sourceText = portal->sourceText;
            if (portal->prepStmtName)
                  prepStmtName = portal->prepStmtName;
            else
                  prepStmtName = "<unnamed>";
            portalParams = portal->portalParams;
      }

      /*
       * Report query to various monitoring facilities.
       */
      debug_query_string = sourceText;

      pgstat_report_activity(sourceText);

      set_ps_display(portal->commandTag, false);

      if (save_log_statement_stats)
            ResetUsage();

      BeginCommand(portal->commandTag, dest);

      /*
       * Create dest receiver in MessageContext (we don't want it in transaction
       * context, because that may get deleted if portal contains VACUUM).
       */
      receiver = CreateDestReceiver(dest);
      if (dest == DestRemoteExecute)
            SetRemoteDestReceiverParams(receiver, portal);

      /*
       * Ensure we are in a transaction command (this should normally be the
       * case already due to prior BIND).
       */
      start_xact_command();

      /*
       * If we re-issue an Execute protocol request against an existing portal,
       * then we are only fetching more rows rather than completely re-executing
       * the query from the start. atStart is never reset for a v3 portal, so we
       * are safe to use this check.
       */
      execute_is_fetch = !portal->atStart;

      /* Log immediately if dictated by log_statement */
      if (check_log_statement(portal->stmts))
      {
            ereport(LOG,
                        (errmsg("%s %s%s%s: %s",
                                    execute_is_fetch ?
                                    _("execute fetch from") :
                                    _("execute"),
                                    prepStmtName,
                                    *portal_name ? "/" : "",
                                    *portal_name ? portal_name : "",
                                    sourceText),
                         errhidestmt(true),
                         errdetail_params(portalParams)));
            was_logged = true;
      }

      /*
       * If we are in aborted transaction state, the only portals we can
       * actually run are those containing COMMIT or ROLLBACK commands.
       */
      if (IsAbortedTransactionBlockState() &&
            !IsTransactionExitStmtList(portal->stmts))
            ereport(ERROR,
                        (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                         errmsg("current transaction is aborted, "
                                    "commands ignored until end of transaction block")));

      /* Check for cancel signal before we start execution */
      CHECK_FOR_INTERRUPTS();

      /*
       * Okay to run the portal.
       */
      if (max_rows <= 0)
            max_rows = FETCH_ALL;

      completed = PortalRun(portal,
                                      max_rows,
                                      true, /* always top level */
                                      receiver,
                                      receiver,
                                      completionTag);

      (*receiver->rDestroy) (receiver);

      if (completed)
      {
            if (is_xact_command)
            {
                  /*
                   * If this was a transaction control statement, commit it.  We
                   * will start a new xact command for the next command (if any).
                   */
                  finish_xact_command();
            }
            else
            {
                  /*
                   * We need a CommandCounterIncrement after every query, except
                   * those that start or end a transaction block.
                   */
                  CommandCounterIncrement();
            }

            /* Send appropriate CommandComplete to client */
            EndCommand(completionTag, dest);
      }
      else
      {
            /* Portal run not complete, so send PortalSuspended */
            if (whereToSendOutput == DestRemote)
                  pq_putemptymessage('s');
      }

      /*
       * Emit duration logging if appropriate.
       */
      switch (check_log_duration(msec_str, was_logged))
      {
            case 1:
                  ereport(LOG,
                              (errmsg("duration: %s ms", msec_str),
                               errhidestmt(true)));
                  break;
            case 2:
                  ereport(LOG,
                              (errmsg("duration: %s ms  %s %s%s%s: %s",
                                          msec_str,
                                          execute_is_fetch ?
                                          _("execute fetch from") :
                                          _("execute"),
                                          prepStmtName,
                                          *portal_name ? "/" : "",
                                          *portal_name ? portal_name : "",
                                          sourceText),
                               errhidestmt(true),
                               errdetail_params(portalParams)));
                  break;
      }

      if (save_log_statement_stats)
            ShowUsage("EXECUTE MESSAGE STATISTICS");

      debug_query_string = NULL;
}

/*
 * check_log_statement
 *          Determine whether command should be logged because of log_statement
 *
 * parsetree_list can be either raw grammar output or a list of planned
 * statements
 */
static bool
check_log_statement(List *stmt_list)
{
      ListCell   *stmt_item;

      if (log_statement == LOGSTMT_NONE)
            return false;
      if (log_statement == LOGSTMT_ALL)
            return true;

      /* Else we have to inspect the statement(s) to see whether to log */
      foreach(stmt_item, stmt_list)
      {
            Node     *stmt = (Node *) lfirst(stmt_item);

            if (GetCommandLogLevel(stmt) <= log_statement)
                  return true;
      }

      return false;
}

/*
 * check_log_duration
 *          Determine whether current command's duration should be logged
 *
 * Returns:
 *          0 if no logging is needed
 *          1 if just the duration should be logged
 *          2 if duration and query details should be logged
 *
 * If logging is needed, the duration in msec is formatted into msec_str[],
 * which must be a 32-byte buffer.
 *
 * was_logged should be TRUE if caller already logged query details (this
 * essentially prevents 2 from being returned).
 */
int
check_log_duration(char *msec_str, bool was_logged)
{
      if (log_duration || log_min_duration_statement >= 0)
      {
            long        secs;
            int               usecs;
            int               msecs;
            bool        exceeded;

            TimestampDifference(GetCurrentStatementStartTimestamp(),
                                          GetCurrentTimestamp(),
                                          &secs, &usecs);
            msecs = usecs / 1000;

            /*
             * This odd-looking test for log_min_duration_statement being exceeded
             * is designed to avoid integer overflow with very long durations:
             * don't compute secs * 1000 until we've verified it will fit in int.
             */
            exceeded = (log_min_duration_statement == 0 ||
                              (log_min_duration_statement > 0 &&
                               (secs > log_min_duration_statement / 1000 ||
                                secs * 1000 + msecs >= log_min_duration_statement)));

            if (exceeded || log_duration)
            {
                  snprintf(msec_str, 32, "%ld.%03d",
                               secs * 1000 + msecs, usecs % 1000);
                  if (exceeded && !was_logged)
                        return 2;
                  else
                        return 1;
            }
      }

      return 0;
}

/*
 * errdetail_execute
 *
 * Add an errdetail() line showing the query referenced by an EXECUTE, if any.
 * The argument is the raw parsetree list.
 */
static int
errdetail_execute(List *raw_parsetree_list)
{
      ListCell   *parsetree_item;

      foreach(parsetree_item, raw_parsetree_list)
      {
            Node     *parsetree = (Node *) lfirst(parsetree_item);

            if (IsA(parsetree, ExecuteStmt))
            {
                  ExecuteStmt *stmt = (ExecuteStmt *) parsetree;
                  PreparedStatement *pstmt;

                  pstmt = FetchPreparedStatement(stmt->name, false);
                  if (pstmt)
                  {
                        errdetail("prepare: %s", pstmt->plansource->query_string);
                        return 0;
                  }
            }
      }

      return 0;
}

/*
 * errdetail_params
 *
 * Add an errdetail() line showing bind-parameter data, if available.
 */
static int
errdetail_params(ParamListInfo params)
{
      /* We mustn't call user-defined I/O functions when in an aborted xact */
      if (params && params->numParams > 0 && !IsAbortedTransactionBlockState())
      {
            StringInfoData param_str;
            MemoryContext oldcontext;
            int               paramno;

            /* Make sure any trash is generated in MessageContext */
            oldcontext = MemoryContextSwitchTo(MessageContext);

            initStringInfo(&param_str);

            for (paramno = 0; paramno < params->numParams; paramno++)
            {
                  ParamExternData *prm = &params->params[paramno];
                  Oid               typoutput;
                  bool        typisvarlena;
                  char     *pstring;
                  char     *p;

                  appendStringInfo(&param_str, "%s$%d = ",
                                           paramno > 0 ? ", " : "",
                                           paramno + 1);

                  if (prm->isnull || !OidIsValid(prm->ptype))
                  {
                        appendStringInfoString(&param_str, "NULL");
                        continue;
                  }

                  getTypeOutputInfo(prm->ptype, &typoutput, &typisvarlena);

                  pstring = OidOutputFunctionCall(typoutput, prm->value);

                  appendStringInfoCharMacro(&param_str, '\'');
                  for (p = pstring; *p; p++)
                  {
                        if (*p == '\'') /* double single quotes */
                              appendStringInfoCharMacro(&param_str, *p);
                        appendStringInfoCharMacro(&param_str, *p);
                  }
                  appendStringInfoCharMacro(&param_str, '\'');

                  pfree(pstring);
            }

            errdetail("parameters: %s", param_str.data);

            pfree(param_str.data);

            MemoryContextSwitchTo(oldcontext);
      }

      return 0;
}

/*
 * exec_describe_statement_message
 *
 * Process a "Describe" message for a prepared statement
 */
static void
exec_describe_statement_message(const char *stmt_name)
{
      CachedPlanSource *psrc;
      StringInfoData buf;
      int               i;

      /*
       * Start up a transaction command. (Note that this will normally change
       * current memory context.) Nothing happens if we are already in one.
       */
      start_xact_command();

      /* Switch back to message context */
      MemoryContextSwitchTo(MessageContext);

      /* Find prepared statement */
      if (stmt_name[0] != '\0')
      {
            PreparedStatement *pstmt;

            pstmt = FetchPreparedStatement(stmt_name, true);
            psrc = pstmt->plansource;
      }
      else
      {
            /* special-case the unnamed statement */
            psrc = unnamed_stmt_psrc;
            if (!psrc)
                  ereport(ERROR,
                              (errcode(ERRCODE_UNDEFINED_PSTATEMENT),
                               errmsg("unnamed prepared statement does not exist")));
      }

      /* Prepared statements shouldn't have changeable result descs */
      Assert(psrc->fixed_result);

      /*
       * If we are in aborted transaction state, we can't run
       * SendRowDescriptionMessage(), because that needs catalog accesses. (We
       * can't do RevalidateCachedPlan, either, but that's a lesser problem.)
       * Hence, refuse to Describe statements that return data.  (We shouldn't
       * just refuse all Describes, since that might break the ability of some
       * clients to issue COMMIT or ROLLBACK commands, if they use code that
       * blindly Describes whatever it does.)  We can Describe parameters
       * without doing anything dangerous, so we don't restrict that.
       */
      if (IsAbortedTransactionBlockState() &&
            psrc->resultDesc)
            ereport(ERROR,
                        (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                         errmsg("current transaction is aborted, "
                                    "commands ignored until end of transaction block")));

      if (whereToSendOutput != DestRemote)
            return;                             /* can't actually do anything... */

      /*
       * First describe the parameters...
       */
      pq_beginmessage(&buf, 't'); /* parameter description message type */
      pq_sendint(&buf, psrc->num_params, 2);

      for (i = 0; i < psrc->num_params; i++)
      {
            Oid               ptype = psrc->param_types[i];

            pq_sendint(&buf, (int) ptype, 4);
      }
      pq_endmessage(&buf);

      /*
       * Next send RowDescription or NoData to describe the result...
       */
      if (psrc->resultDesc)
      {
            CachedPlan *cplan;
            List     *tlist;

            /* Make sure the plan is up to date */
            cplan = RevalidateCachedPlan(psrc, true);

            /* Get the primary statement and find out what it returns */
            tlist = FetchStatementTargetList(PortalListGetPrimaryStmt(cplan->stmt_list));

            SendRowDescriptionMessage(psrc->resultDesc, tlist, NULL);

            ReleaseCachedPlan(cplan, true);
      }
      else
            pq_putemptymessage('n');      /* NoData */

}

/*
 * exec_describe_portal_message
 *
 * Process a "Describe" message for a portal
 */
static void
exec_describe_portal_message(const char *portal_name)
{
      Portal            portal;

      /*
       * Start up a transaction command. (Note that this will normally change
       * current memory context.) Nothing happens if we are already in one.
       */
      start_xact_command();

      /* Switch back to message context */
      MemoryContextSwitchTo(MessageContext);

      portal = GetPortalByName(portal_name);
      if (!PortalIsValid(portal))
            ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_CURSOR),
                         errmsg("portal \"%s\" does not exist", portal_name)));

      /*
       * If we are in aborted transaction state, we can't run
       * SendRowDescriptionMessage(), because that needs catalog accesses.
       * Hence, refuse to Describe portals that return data.      (We shouldn't just
       * refuse all Describes, since that might break the ability of some
       * clients to issue COMMIT or ROLLBACK commands, if they use code that
       * blindly Describes whatever it does.)
       */
      if (IsAbortedTransactionBlockState() &&
            portal->tupDesc)
            ereport(ERROR,
                        (errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
                         errmsg("current transaction is aborted, "
                                    "commands ignored until end of transaction block")));

      if (whereToSendOutput != DestRemote)
            return;                             /* can't actually do anything... */

      if (portal->tupDesc)
            SendRowDescriptionMessage(portal->tupDesc,
                                                  FetchPortalTargetList(portal),
                                                  portal->formats);
      else
            pq_putemptymessage('n');      /* NoData */
}


/*
 * Convenience routines for starting/committing a single command.
 */
static void
start_xact_command(void)
{
      if (!xact_started)
      {
            ereport(DEBUG3,
                        (errmsg_internal("StartTransactionCommand")));
            StartTransactionCommand();

            /* Set statement timeout running, if any */
            /* NB: this mustn't be enabled until we are within an xact */
            if (StatementTimeout > 0)
                  enable_sig_alarm(StatementTimeout, true);
            else
                  cancel_from_timeout = false;

            xact_started = true;
      }
}

static void
finish_xact_command(void)
{
      if (xact_started)
      {
            /* Cancel any active statement timeout before committing */
            disable_sig_alarm(true);

            /* Now commit the command */
            ereport(DEBUG3,
                        (errmsg_internal("CommitTransactionCommand")));

            CommitTransactionCommand();

#ifdef MEMORY_CONTEXT_CHECKING
            /* Check all memory contexts that weren't freed during commit */
            /* (those that were, were checked before being deleted) */
            MemoryContextCheck(TopMemoryContext);
#endif

#ifdef SHOW_MEMORY_STATS
            /* Print mem stats after each commit for leak tracking */
            MemoryContextStats(TopMemoryContext);
#endif

            xact_started = false;
      }
}


/*
 * Convenience routines for checking whether a statement is one of the
 * ones that we allow in transaction-aborted state.
 */

/* Test a bare parsetree */
static bool
IsTransactionExitStmt(Node *parsetree)
{
      if (parsetree && IsA(parsetree, TransactionStmt))
      {
            TransactionStmt *stmt = (TransactionStmt *) parsetree;

            if (stmt->kind == TRANS_STMT_COMMIT ||
                  stmt->kind == TRANS_STMT_PREPARE ||
                  stmt->kind == TRANS_STMT_ROLLBACK ||
                  stmt->kind == TRANS_STMT_ROLLBACK_TO)
                  return true;
      }
      return false;
}

/* Test a list that might contain Query nodes or bare parsetrees */
static bool
IsTransactionExitStmtList(List *parseTrees)
{
      if (list_length(parseTrees) == 1)
      {
            Node     *stmt = (Node *) linitial(parseTrees);

            if (IsA(stmt, Query))
            {
                  Query    *query = (Query *) stmt;

                  if (query->commandType == CMD_UTILITY &&
                        IsTransactionExitStmt(query->utilityStmt))
                        return true;
            }
            else if (IsTransactionExitStmt(stmt))
                  return true;
      }
      return false;
}

/* Test a list that might contain Query nodes or bare parsetrees */
static bool
IsTransactionStmtList(List *parseTrees)
{
      if (list_length(parseTrees) == 1)
      {
            Node     *stmt = (Node *) linitial(parseTrees);

            if (IsA(stmt, Query))
            {
                  Query    *query = (Query *) stmt;

                  if (query->commandType == CMD_UTILITY &&
                        IsA(query->utilityStmt, TransactionStmt))
                        return true;
            }
            else if (IsA(stmt, TransactionStmt))
                  return true;
      }
      return false;
}

/* Release any existing unnamed prepared statement */
static void
drop_unnamed_stmt(void)
{
      /* Release any completed unnamed statement */
      if (unnamed_stmt_psrc)
            DropCachedPlan(unnamed_stmt_psrc);
      unnamed_stmt_psrc = NULL;

      /*
       * If we failed while trying to build a prior unnamed statement, we may
       * have a memory context that wasn't assigned to a completed plancache
       * entry.  If so, drop it to avoid a permanent memory leak.
       */
      if (unnamed_stmt_context)
            MemoryContextDelete(unnamed_stmt_context);
      unnamed_stmt_context = NULL;
}


/* --------------------------------
 *          signal handler routines used in PostgresMain()
 * --------------------------------
 */

/*
 * quickdie() occurs when signalled SIGQUIT by the postmaster.
 *
 * Some backend has bought the farm,
 * so we need to stop what we're doing and exit.
 */
void
quickdie(SIGNAL_ARGS)
{
      PG_SETMASK(&BlockSig);

      /*
       * Ideally this should be ereport(FATAL), but then we'd not get control
       * back...
       */
      ereport(WARNING,
                  (errcode(ERRCODE_CRASH_SHUTDOWN),
                   errmsg("terminating connection because of crash of another server process"),
      errdetail("The postmaster has commanded this server process to roll back"
                    " the current transaction and exit, because another"
                    " server process exited abnormally and possibly corrupted"
                    " shared memory."),
                   errhint("In a moment you should be able to reconnect to the"
                               " database and repeat your command.")));

      /*
       * We DO NOT want to run proc_exit() callbacks -- we're here because
       * shared memory may be corrupted, so we don't want to try to clean up our
       * transaction.  Just nail the windows shut and get out of town.  Now that
       * there's an atexit callback to prevent third-party code from breaking
       * things by calling exit() directly, we have to reset the callbacks
       * explicitly to make this work as intended.
       */
      on_exit_reset();

      /*
       * Note we do exit(2) not exit(0).  This is to force the postmaster into a
       * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
       * backend.  This is necessary precisely because we don't clean up our
       * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
       * should ensure the postmaster sees this as a crash, too, but no harm in
       * being doubly sure.)
       */
      exit(2);
}

/*
 * Shutdown signal from postmaster: abort transaction and exit
 * at soonest convenient time
 */
void
die(SIGNAL_ARGS)
{
      int               save_errno = errno;

      /* Don't joggle the elbow of proc_exit */
      if (!proc_exit_inprogress)
      {
            InterruptPending = true;
            ProcDiePending = true;

            /*
             * If it's safe to interrupt, and we're waiting for input or a lock,
             * service the interrupt immediately
             */
            if (ImmediateInterruptOK && InterruptHoldoffCount == 0 &&
                  CritSectionCount == 0)
            {
                  /* bump holdoff count to make ProcessInterrupts() a no-op */
                  /* until we are done getting ready for it */
                  InterruptHoldoffCount++;
                  LockWaitCancel(); /* prevent CheckDeadLock from running */
                  DisableNotifyInterrupt();
                  DisableCatchupInterrupt();
                  InterruptHoldoffCount--;
                  ProcessInterrupts();
            }
      }

      errno = save_errno;
}

/*
 * Timeout or shutdown signal from postmaster during client authentication.
 * Simply exit(1).
 *
 * XXX: possible future improvement: try to send a message indicating
 * why we are disconnecting.  Problem is to be sure we don't block while
 * doing so, nor mess up the authentication message exchange.
 */
void
authdie(SIGNAL_ARGS)
{
      proc_exit(1);
}

/*
 * Query-cancel signal from postmaster: abort current transaction
 * at soonest convenient time
 */
void
StatementCancelHandler(SIGNAL_ARGS)
{
      int               save_errno = errno;

      /*
       * Don't joggle the elbow of proc_exit
       */
      if (!proc_exit_inprogress)
      {
            InterruptPending = true;
            QueryCancelPending = true;

            /*
             * If it's safe to interrupt, and we're waiting for a lock, service
             * the interrupt immediately.  No point in interrupting if we're
             * waiting for input, however.
             */
            if (ImmediateInterruptOK && InterruptHoldoffCount == 0 &&
                  CritSectionCount == 0 && !DoingCommandRead)
            {
                  /* bump holdoff count to make ProcessInterrupts() a no-op */
                  /* until we are done getting ready for it */
                  InterruptHoldoffCount++;
                  LockWaitCancel(); /* prevent CheckDeadLock from running */
                  DisableNotifyInterrupt();
                  DisableCatchupInterrupt();
                  InterruptHoldoffCount--;
                  ProcessInterrupts();
            }
      }

      errno = save_errno;
}

/* signal handler for floating point exception */
void
FloatExceptionHandler(SIGNAL_ARGS)
{
      ereport(ERROR,
                  (errcode(ERRCODE_FLOATING_POINT_EXCEPTION),
                   errmsg("floating-point exception"),
                   errdetail("An invalid floating-point operation was signaled. "
                                 "This probably means an out-of-range result or an "
                                 "invalid operation, such as division by zero.")));
}

/* SIGHUP: set flag to re-read config file at next convenient time */
static void
SigHupHandler(SIGNAL_ARGS)
{
      got_SIGHUP = true;
}


/*
 * ProcessInterrupts: out-of-line portion of CHECK_FOR_INTERRUPTS() macro
 *
 * If an interrupt condition is pending, and it's safe to service it,
 * then clear the flag and accept the interrupt.  Called only when
 * InterruptPending is true.
 */
void
ProcessInterrupts(void)
{
      /* OK to accept interrupt now? */
      if (InterruptHoldoffCount != 0 || CritSectionCount != 0)
            return;
      InterruptPending = false;
      if (ProcDiePending)
      {
            ProcDiePending = false;
            QueryCancelPending = false;         /* ProcDie trumps QueryCancel */
            ImmediateInterruptOK = false; /* not idle anymore */
            DisableNotifyInterrupt();
            DisableCatchupInterrupt();
            if (IsAutoVacuumWorkerProcess())
                  ereport(FATAL,
                              (errcode(ERRCODE_ADMIN_SHUTDOWN),
                               errmsg("terminating autovacuum process due to administrator command")));
            else
                  ereport(FATAL,
                              (errcode(ERRCODE_ADMIN_SHUTDOWN),
                   errmsg("terminating connection due to administrator command")));
      }
      if (QueryCancelPending)
      {
            QueryCancelPending = false;
            ImmediateInterruptOK = false; /* not idle anymore */
            DisableNotifyInterrupt();
            DisableCatchupInterrupt();
            if (cancel_from_timeout)
                  ereport(ERROR,
                              (errcode(ERRCODE_QUERY_CANCELED),
                               errmsg("canceling statement due to statement timeout")));
            else if (IsAutoVacuumWorkerProcess())
                  ereport(ERROR,
                              (errcode(ERRCODE_QUERY_CANCELED),
                               errmsg("canceling autovacuum task")));
            else
                  ereport(ERROR,
                              (errcode(ERRCODE_QUERY_CANCELED),
                               errmsg("canceling statement due to user request")));
      }
      /* If we get here, do nothing (probably, QueryCancelPending was reset) */
}


/*
 * check_stack_depth: check for excessively deep recursion
 *
 * This should be called someplace in any recursive routine that might possibly
 * recurse deep enough to overflow the stack.  Most Unixen treat stack
 * overflow as an unrecoverable SIGSEGV, so we want to error out ourselves
 * before hitting the hardware limit.
 */
void
check_stack_depth(void)
{
      char        stack_top_loc;
      long        stack_depth;

      /*
       * Compute distance from PostgresMain's local variables to my own
       */
      stack_depth = (long) (stack_base_ptr - &stack_top_loc);

      /*
       * Take abs value, since stacks grow up on some machines, down on others
       */
      if (stack_depth < 0)
            stack_depth = -stack_depth;

      /*
       * Trouble?
       *
       * The test on stack_base_ptr prevents us from erroring out if called
       * during process setup or in a non-backend process.  Logically it should
       * be done first, but putting it here avoids wasting cycles during normal
       * cases.
       */
      if (stack_depth > max_stack_depth_bytes &&
            stack_base_ptr != NULL)
      {
            ereport(ERROR,
                        (errcode(ERRCODE_STATEMENT_TOO_COMPLEX),
                         errmsg("stack depth limit exceeded"),
             errhint("Increase the configuration parameter \"max_stack_depth\", "
               "after ensuring the platform's stack depth limit is adequate.")));
      }
}

/* GUC assign hook for max_stack_depth */
bool
assign_max_stack_depth(int newval, bool doit, GucSource source)
{
      long        newval_bytes = newval * 1024L;
      long        stack_rlimit = get_stack_depth_rlimit();

      if (stack_rlimit > 0 && newval_bytes > stack_rlimit - STACK_DEPTH_SLOP)
      {
            ereport(GUC_complaint_elevel(source),
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("\"max_stack_depth\" must not exceed %ldkB",
                                    (stack_rlimit - STACK_DEPTH_SLOP) / 1024L),
                         errhint("Increase the platform's stack depth limit via \"ulimit -s\" or local equivalent.")));
            return false;
      }
      if (doit)
            max_stack_depth_bytes = newval_bytes;
      return true;
}


/*
 * set_debug_options --- apply "-d N" command line option
 *
 * -d is not quite the same as setting log_min_messages because it enables
 * other output options.
 */
void
set_debug_options(int debug_flag, GucContext context, GucSource source)
{
      if (debug_flag > 0)
      {
            char        debugstr[64];

            sprintf(debugstr, "debug%d", debug_flag);
            SetConfigOption("log_min_messages", debugstr, context, source);
      }
      else
            SetConfigOption("log_min_messages", "notice", context, source);

      if (debug_flag >= 1 && context == PGC_POSTMASTER)
      {
            SetConfigOption("log_connections", "true", context, source);
            SetConfigOption("log_disconnections", "true", context, source);
      }
      if (debug_flag >= 2)
            SetConfigOption("log_statement", "all", context, source);
      if (debug_flag >= 3)
            SetConfigOption("debug_print_parse", "true", context, source);
      if (debug_flag >= 4)
            SetConfigOption("debug_print_plan", "true", context, source);
      if (debug_flag >= 5)
            SetConfigOption("debug_print_rewritten", "true", context, source);
}


bool
set_plan_disabling_options(const char *arg, GucContext context, GucSource source)
{
      char     *tmp = NULL;

      switch (arg[0])
      {
            case 's':                     /* seqscan */
                  tmp = "enable_seqscan";
                  break;
            case 'i':                     /* indexscan */
                  tmp = "enable_indexscan";
                  break;
            case 'b':                     /* bitmapscan */
                  tmp = "enable_bitmapscan";
                  break;
            case 't':                     /* tidscan */
                  tmp = "enable_tidscan";
                  break;
            case 'n':                     /* nestloop */
                  tmp = "enable_nestloop";
                  break;
            case 'm':                     /* mergejoin */
                  tmp = "enable_mergejoin";
                  break;
            case 'h':                     /* hashjoin */
                  tmp = "enable_hashjoin";
                  break;
      }
      if (tmp)
      {
            SetConfigOption(tmp, "false", context, source);
            return true;
      }
      else
            return false;
}


const char *
get_stats_option_name(const char *arg)
{
      switch (arg[0])
      {
            case 'p':
                  if (optarg[1] == 'a')         /* "parser" */
                        return "log_parser_stats";
                  else if (optarg[1] == 'l')    /* "planner" */
                        return "log_planner_stats";
                  break;

            case 'e':                     /* "executor" */
                  return "log_executor_stats";
                  break;
      }

      return NULL;
}


/* ----------------------------------------------------------------
 * PostgresMain
 *       postgres main loop -- all backends, interactive or otherwise start here
 *
 * argc/argv are the command line arguments to be used.  (When being forked
 * by the postmaster, these are not the original argv array of the process.)
 * username is the (possibly authenticated) PostgreSQL user name to be used
 * for the session.
 * ----------------------------------------------------------------
 */
int
PostgresMain(int argc, char *argv[], const char *username)
{
      int               flag;
      const char *dbname = NULL;
      char     *userDoption = NULL;
      bool        secure;
      int               errs = 0;
      int               debug_flag = -1;  /* -1 means not given */
      List     *guc_names = NIL;    /* for SUSET options */
      List     *guc_values = NIL;
      GucContext  ctx;
      GucSource   gucsource;
      bool        am_superuser;
      int               firstchar;
      char        stack_base;
      StringInfoData input_message;
      sigjmp_buf  local_sigjmp_buf;
      volatile bool send_ready_for_query = true;

#define PendingConfigOption(name,val) \
      (guc_names = lappend(guc_names, pstrdup(name)), \
       guc_values = lappend(guc_values, pstrdup(val)))

      /*
       * initialize globals (already done if under postmaster, but not if
       * standalone; cheap enough to do over)
       */
      MyProcPid = getpid();

      MyStartTime = time(NULL);

      /*
       * Fire up essential subsystems: error and memory management
       *
       * If we are running under the postmaster, this is done already.
       */
      if (!IsUnderPostmaster)
            MemoryContextInit();

      set_ps_display("startup", false);

      SetProcessingMode(InitProcessing);

      /* Set up reference point for stack depth checking */
      stack_base_ptr = &stack_base;

      /* Compute paths, if we didn't inherit them from postmaster */
      if (my_exec_path[0] == '\0')
      {
            if (find_my_exec(argv[0], my_exec_path) < 0)
                  elog(FATAL, "%s: could not locate my own executable path",
                         argv[0]);
      }

      if (pkglib_path[0] == '\0')
            get_pkglib_path(my_exec_path, pkglib_path);

      /*
       * Set default values for command-line options.
       */
      EchoQuery = false;

      if (!IsUnderPostmaster)
            InitializeGUCOptions();

      /* ----------------
       *    parse command line arguments
       *
       *    There are now two styles of command line layout for the backend:
       *
       *    For interactive use (not started from postmaster) the format is
       *          postgres [switches] [databasename]
       *    If the databasename is omitted it is taken to be the user name.
       *
       *    When started from the postmaster, the format is
       *          postgres [secure switches] -y databasename [insecure switches]
       *    Switches appearing after -y came from the client (via "options"
       *    field of connection request).  For security reasons we restrict
       *    what these switches can do.
       * ----------------
       */

      /* Ignore the initial --single argument, if present */
      if (argc > 1 && strcmp(argv[1], "--single") == 0)
      {
            argv++;
            argc--;
      }

      /* all options are allowed until '-y' */
      secure = true;
      ctx = PGC_POSTMASTER;
      gucsource = PGC_S_ARGV;       /* initial switches came from command line */

      /*
       * Parse command-line options.      CAUTION: keep this in sync with
       * postmaster/postmaster.c (the option sets should not conflict) and with
       * the common help() function in main/main.c.
       */
      while ((flag = getopt(argc, argv, "A:B:c:D:d:EeFf:h:ijk:lN:nOo:Pp:r:S:sTt:v:W:y:-:")) != -1)
      {
            switch (flag)
            {
                  case 'A':
                        SetConfigOption("debug_assertions", optarg, ctx, gucsource);
                        break;

                  case 'B':
                        SetConfigOption("shared_buffers", optarg, ctx, gucsource);
                        break;

                  case 'D':
                        if (secure)
                              userDoption = optarg;
                        break;

                  case 'd':
                        debug_flag = atoi(optarg);
                        break;

                  case 'E':
                        EchoQuery = true;
                        break;

                  case 'e':
                        SetConfigOption("datestyle", "euro", ctx, gucsource);
                        break;

                  case 'F':
                        SetConfigOption("fsync", "false", ctx, gucsource);
                        break;

                  case 'f':
                        if (!set_plan_disabling_options(optarg, ctx, gucsource))
                              errs++;
                        break;

                  case 'h':
                        SetConfigOption("listen_addresses", optarg, ctx, gucsource);
                        break;

                  case 'i':
                        SetConfigOption("listen_addresses", "*", ctx, gucsource);
                        break;

                  case 'j':
                        UseNewLine = 0;
                        break;

                  case 'k':
                        SetConfigOption("unix_socket_directory", optarg, ctx, gucsource);
                        break;

                  case 'l':
                        SetConfigOption("ssl", "true", ctx, gucsource);
                        break;

                  case 'N':
                        SetConfigOption("max_connections", optarg, ctx, gucsource);
                        break;

                  case 'n':
                        /* ignored for consistency with postmaster */
                        break;

                  case 'O':
                        SetConfigOption("allow_system_table_mods", "true", ctx, gucsource);
                        break;

                  case 'o':
                        errs++;
                        break;

                  case 'P':
                        SetConfigOption("ignore_system_indexes", "true", ctx, gucsource);
                        break;

                  case 'p':
                        SetConfigOption("port", optarg, ctx, gucsource);
                        break;

                  case 'r':
                        /* send output (stdout and stderr) to the given file */
                        if (secure)
                              strlcpy(OutputFileName, optarg, MAXPGPATH);
                        break;

                  case 'S':
                        SetConfigOption("work_mem", optarg, ctx, gucsource);
                        break;

                  case 's':

                        /*
                         * Since log options are SUSET, we need to postpone unless
                         * still in secure context
                         */
                        if (ctx == PGC_BACKEND)
                              PendingConfigOption("log_statement_stats", "true");
                        else
                              SetConfigOption("log_statement_stats", "true",
                                                      ctx, gucsource);
                        break;

                  case 'T':
                        /* ignored for consistency with postmaster */
                        break;

                  case 't':
                        {
                              const char *tmp = get_stats_option_name(optarg);

                              if (tmp)
                              {
                                    if (ctx == PGC_BACKEND)
                                          PendingConfigOption(tmp, "true");
                                    else
                                          SetConfigOption(tmp, "true", ctx, gucsource);
                              }
                              else
                                    errs++;
                              break;
                        }

                  case 'v':
                        if (secure)
                              FrontendProtocol = (ProtocolVersion) atoi(optarg);
                        break;

                  case 'W':
                        SetConfigOption("post_auth_delay", optarg, ctx, gucsource);
                        break;


                  case 'y':

                        /*
                         * y - special flag passed if backend was forked by a
                         * postmaster.
                         */
                        if (secure)
                        {
                              dbname = strdup(optarg);

                              secure = false;         /* subsequent switches are NOT secure */
                              ctx = PGC_BACKEND;
                              gucsource = PGC_S_CLIENT;
                        }
                        break;

                  case 'c':
                  case '-':
                        {
                              char     *name,
                                             *value;

                              ParseLongOption(optarg, &name, &value);
                              if (!value)
                              {
                                    if (flag == '-')
                                          ereport(ERROR,
                                                      (errcode(ERRCODE_SYNTAX_ERROR),
                                                       errmsg("--%s requires a value",
                                                                  optarg)));
                                    else
                                          ereport(ERROR,
                                                      (errcode(ERRCODE_SYNTAX_ERROR),
                                                       errmsg("-c %s requires a value",
                                                                  optarg)));
                              }

                              /*
                               * If a SUSET option, must postpone evaluation, unless we
                               * are still reading secure switches.
                               */
                              if (ctx == PGC_BACKEND && IsSuperuserConfigOption(name))
                                    PendingConfigOption(name, value);
                              else
                                    SetConfigOption(name, value, ctx, gucsource);
                              free(name);
                              if (value)
                                    free(value);
                              break;
                        }

                  default:
                        errs++;
                        break;
            }
      }

      /*
       * Process any additional GUC variable settings passed in startup packet.
       * These are handled exactly like command-line variables.
       */
      if (MyProcPort != NULL)
      {
            ListCell   *gucopts = list_head(MyProcPort->guc_options);

            while (gucopts)
            {
                  char     *name;
                  char     *value;

                  name = lfirst(gucopts);
                  gucopts = lnext(gucopts);

                  value = lfirst(gucopts);
                  gucopts = lnext(gucopts);

                  if (IsSuperuserConfigOption(name))
                        PendingConfigOption(name, value);
                  else
                        SetConfigOption(name, value, PGC_BACKEND, PGC_S_CLIENT);
            }
      }

      /* Acquire configuration parameters, unless inherited from postmaster */
      if (!IsUnderPostmaster)
      {
            if (!SelectConfigFiles(userDoption, argv[0]))
                  proc_exit(1);
            /* If timezone is not set, determine what the OS uses */
            pg_timezone_initialize();
            /* If timezone_abbreviations is not set, select default */
            pg_timezone_abbrev_initialize();
      }

      if (PostAuthDelay)
            pg_usleep(PostAuthDelay * 1000000L);

      /*
       * You might expect to see a setsid() call here, but it's not needed,
       * because if we are under a postmaster then BackendInitialize() did it.
       */

      /*
       * Set up signal handlers and masks.
       *
       * Note that postmaster blocked all signals before forking child process,
       * so there is no race condition whereby we might receive a signal before
       * we have set up the handler.
       *
       * Also note: it's best not to use any signals that are SIG_IGNored in the
       * postmaster.    If such a signal arrives before we are able to change the
       * handler to non-SIG_IGN, it'll get dropped.  Instead, make a dummy
       * handler in the postmaster to reserve the signal. (Of course, this isn't
       * an issue for signals that are locally generated, such as SIGALRM and
       * SIGPIPE.)
       */
      pqsignal(SIGHUP, SigHupHandler);    /* set flag to read config file */
      pqsignal(SIGINT, StatementCancelHandler); /* cancel current query */
      pqsignal(SIGTERM, die);       /* cancel current query and exit */

      /*
       * In a standalone backend, SIGQUIT can be generated from the keyboard
       * easily, while SIGTERM cannot, so we make both signals do die() rather
       * than quickdie().
       */
      if (IsUnderPostmaster)
            pqsignal(SIGQUIT, quickdie);  /* hard crash time */
      else
            pqsignal(SIGQUIT, die); /* cancel current query and exit */
      pqsignal(SIGALRM, handle_sig_alarm);            /* timeout conditions */

      /*
       * Ignore failure to write to frontend. Note: if frontend closes
       * connection, we will notice it and exit cleanly when control next
       * returns to outer loop.  This seems safer than forcing exit in the midst
       * of output during who-knows-what operation...
       */
      pqsignal(SIGPIPE, SIG_IGN);
      pqsignal(SIGUSR1, CatchupInterruptHandler);
      pqsignal(SIGUSR2, NotifyInterruptHandler);
      pqsignal(SIGFPE, FloatExceptionHandler);

      /*
       * Reset some signals that are accepted by postmaster but not by backend
       */
      pqsignal(SIGCHLD, SIG_DFL); /* system() requires this on some platforms */

      pqinitmask();

      if (IsUnderPostmaster)
      {
            /* We allow SIGQUIT (quickdie) at all times */
#ifdef HAVE_SIGPROCMASK
            sigdelset(&BlockSig, SIGQUIT);
#else
            BlockSig &= ~(sigmask(SIGQUIT));
#endif
      }

      PG_SETMASK(&BlockSig);        /* block everything except SIGQUIT */

      if (IsUnderPostmaster)
      {
            /* noninteractive case: nothing should be left after switches */
            if (errs || argc != optind || dbname == NULL)
            {
                  ereport(FATAL,
                              (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("invalid command-line arguments for server process"),
                     errhint("Try \"%s --help\" for more information.", argv[0])));
            }

            BaseInit();
      }
      else
      {
            /* interactive case: database name can be last arg on command line */
            if (errs || argc - optind > 1)
            {
                  ereport(FATAL,
                              (errcode(ERRCODE_SYNTAX_ERROR),
                               errmsg("%s: invalid command-line arguments",
                                          argv[0]),
                     errhint("Try \"%s --help\" for more information.", argv[0])));
            }
            else if (argc - optind == 1)
                  dbname = argv[optind];
            else if ((dbname = username) == NULL)
            {
                  ereport(FATAL,
                              (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                               errmsg("%s: no database nor user name specified",
                                          argv[0])));
            }

            /*
             * Validate we have been given a reasonable-looking DataDir (if under
             * postmaster, assume postmaster did this already).
             */
            Assert(DataDir);
            ValidatePgVersion(DataDir);

            /* Change into DataDir (if under postmaster, was done already) */
            ChangeToDataDir();

            /*
             * Create lockfile for data directory.
             */
            CreateDataDirLockFile(false);

            BaseInit();

            /*
             * Start up xlog for standalone backend, and register to have it
             * closed down at exit.
             */
            StartupXLOG();
            on_shmem_exit(ShutdownXLOG, 0);

            /*
             * We have to build the flat file for pg_database, but not for the
             * user and group tables, since we won't try to do authentication.
             */
            BuildFlatFiles(true);
      }

      /*
       * Create a per-backend PGPROC struct in shared memory, except in the
       * EXEC_BACKEND case where this was done in SubPostmasterMain. We must do
       * this before we can use LWLocks (and in the EXEC_BACKEND case we already
       * had to do some stuff with LWLocks).
       */
#ifdef EXEC_BACKEND
      if (!IsUnderPostmaster)
            InitProcess();
#else
      InitProcess();
#endif

      /*
       * General initialization.
       *
       * NOTE: if you are tempted to add code in this vicinity, consider putting
       * it inside InitPostgres() instead.  In particular, anything that
       * involves database access should be there, not here.
       */
      ereport(DEBUG3,
                  (errmsg_internal("InitPostgres")));
      am_superuser = InitPostgres(dbname, InvalidOid, username, NULL);

      SetProcessingMode(NormalProcessing);

      /*
       * Now that we know if client is a superuser, we can try to apply SUSET
       * GUC options that came from the client.
       */
      ctx = am_superuser ? PGC_SUSET : PGC_USERSET;

      if (debug_flag >= 0)
            set_debug_options(debug_flag, ctx, PGC_S_CLIENT);

      if (guc_names != NIL)
      {
            ListCell   *namcell,
                           *valcell;

            forboth(namcell, guc_names, valcell, guc_values)
            {
                  char     *name = (char *) lfirst(namcell);
                  char     *value = (char *) lfirst(valcell);

                  SetConfigOption(name, value, ctx, PGC_S_CLIENT);
                  pfree(name);
                  pfree(value);
            }
      }

      /*
       * Now all GUC states are fully set up.  Report them to client if
       * appropriate.
       */
      BeginReportingGUCOptions();

      /*
       * Also set up handler to log session end; we have to wait till now to be
       * sure Log_disconnections has its final value.
       */
      if (IsUnderPostmaster && Log_disconnections)
            on_proc_exit(log_disconnections, 0);

      /*
       * process any libraries that should be preloaded at backend start (this
       * likewise can't be done until GUC settings are complete)
       */
      process_local_preload_libraries();

      /*
       * Send this backend's cancellation info to the frontend.
       */
      if (whereToSendOutput == DestRemote &&
            PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
      {
            StringInfoData buf;

            pq_beginmessage(&buf, 'K');
            pq_sendint(&buf, (int32) MyProcPid, sizeof(int32));
            pq_sendint(&buf, (int32) MyCancelKey, sizeof(int32));
            pq_endmessage(&buf);
            /* Need not flush since ReadyForQuery will do it. */
      }

      /* Welcome banner for standalone case */
      if (whereToSendOutput == DestDebug)
            printf("\nPostgreSQL stand-alone backend %s\n", PG_VERSION);

      /*
       * Create the memory context we will use in the main loop.
       *
       * MessageContext is reset once per iteration of the main loop, ie, upon
       * completion of processing of each command message from the client.
       */
      MessageContext = AllocSetContextCreate(TopMemoryContext,
                                                               "MessageContext",
                                                               ALLOCSET_DEFAULT_MINSIZE,
                                                               ALLOCSET_DEFAULT_INITSIZE,
                                                               ALLOCSET_DEFAULT_MAXSIZE);

      /*
       * Remember stand-alone backend startup time
       */
      if (!IsUnderPostmaster)
            PgStartTime = GetCurrentTimestamp();

      /*
       * POSTGRES main processing loop begins here
       *
       * If an exception is encountered, processing resumes here so we abort the
       * current transaction and start a new one.
       *
       * You might wonder why this isn't coded as an infinite loop around a
       * PG_TRY construct.  The reason is that this is the bottom of the
       * exception stack, and so with PG_TRY there would be no exception handler
       * in force at all during the CATCH part.  By leaving the outermost setjmp
       * always active, we have at least some chance of recovering from an error
       * during error recovery.  (If we get into an infinite loop thereby, it
       * will soon be stopped by overflow of elog.c's internal state stack.)
       */

      if (sigsetjmp(local_sigjmp_buf, 1) != 0)
      {
            /*
             * NOTE: if you are tempted to add more code in this if-block,
             * consider the high probability that it should be in
             * AbortTransaction() instead.      The only stuff done directly here
             * should be stuff that is guaranteed to apply *only* for outer-level
             * error recovery, such as adjusting the FE/BE protocol status.
             */

            /* Since not using PG_TRY, must reset error stack by hand */
            error_context_stack = NULL;

            /* Prevent interrupts while cleaning up */
            HOLD_INTERRUPTS();

            /*
             * Forget any pending QueryCancel request, since we're returning to
             * the idle loop anyway, and cancel the statement timer if running.
             */
            QueryCancelPending = false;
            disable_sig_alarm(true);
            QueryCancelPending = false;         /* again in case timeout occurred */

            /*
             * Turn off these interrupts too.  This is only needed here and not in
             * other exception-catching places since these interrupts are only
             * enabled while we wait for client input.
             */
            DoingCommandRead = false;
            DisableNotifyInterrupt();
            DisableCatchupInterrupt();

            /* Make sure libpq is in a good state */
            pq_comm_reset();

            /* Report the error to the client and/or server log */
            EmitErrorReport();

            /*
             * Make sure debug_query_string gets reset before we possibly clobber
             * the storage it points at.
             */
            debug_query_string = NULL;

            /*
             * Abort the current transaction in order to recover.
             */
            AbortCurrentTransaction();

            /*
             * Now return to normal top-level context and clear ErrorContext for
             * next time.
             */
            MemoryContextSwitchTo(TopMemoryContext);
            FlushErrorState();

            /*
             * If we were handling an extended-query-protocol message, initiate
             * skip till next Sync.  This also causes us not to issue
             * ReadyForQuery (until we get Sync).
             */
            if (doing_extended_query_message)
                  ignore_till_sync = true;

            /* We don't have a transaction command open anymore */
            xact_started = false;

            /* Now we can allow interrupts again */
            RESUME_INTERRUPTS();
      }

      /* We can now handle ereport(ERROR) */
      PG_exception_stack = &local_sigjmp_buf;

      PG_SETMASK(&UnBlockSig);

      if (!ignore_till_sync)
            send_ready_for_query = true;  /* initially, or after error */

      /*
       * Non-error queries loop here.
       */

      for (;;)
      {
            /*
             * At top of loop, reset extended-query-message flag, so that any
             * errors encountered in "idle" state don't provoke skip.
             */
            doing_extended_query_message = false;

            /*
             * Release storage left over from prior query cycle, and create a new
             * query input buffer in the cleared MessageContext.
             */
            MemoryContextSwitchTo(MessageContext);
            MemoryContextResetAndDeleteChildren(MessageContext);

            initStringInfo(&input_message);

            /*
             * (1) If we've reached idle state, tell the frontend we're ready for
             * a new query.
             *
             * Note: this includes fflush()'ing the last of the prior output.
             *
             * This is also a good time to send collected statistics to the
             * collector, and to update the PS stats display.  We avoid doing
             * those every time through the message loop because it'd slow down
             * processing of batched messages, and because we don't want to report
             * uncommitted updates (that confuses autovacuum).
             */
            if (send_ready_for_query)
            {
                  if (IsTransactionOrTransactionBlock())
                  {
                        set_ps_display("idle in transaction", false);
                        pgstat_report_activity("<IDLE> in transaction");
                  }
                  else
                  {
                        pgstat_report_stat(false);

                        set_ps_display("idle", false);
                        pgstat_report_activity("<IDLE>");
                  }

                  ReadyForQuery(whereToSendOutput);
                  send_ready_for_query = false;
            }

            /*
             * (2) Allow asynchronous signals to be executed immediately if they
             * come in while we are waiting for client input. (This must be
             * conditional since we don't want, say, reads on behalf of COPY FROM
             * STDIN doing the same thing.)
             */
            QueryCancelPending = false;         /* forget any earlier CANCEL signal */
            DoingCommandRead = true;

            /*
             * (3) read a command (loop blocks here)
             */
            firstchar = ReadCommand(&input_message);

            /*
             * (4) disable async signal conditions again.
             */
            DoingCommandRead = false;

            /*
             * (5) check for any other interesting events that happened while we
             * slept.
             */
            if (got_SIGHUP)
            {
                  got_SIGHUP = false;
                  ProcessConfigFile(PGC_SIGHUP);
            }

            /*
             * (6) process the command.  But ignore it if we're skipping till
             * Sync.
             */
            if (ignore_till_sync && firstchar != EOF)
                  continue;

            switch (firstchar)
            {
                  case 'Q':               /* simple query */
                        {
                              const char *query_string;

                              /* Set statement_timestamp() */
                              SetCurrentStatementStartTimestamp();

                              query_string = pq_getmsgstring(&input_message);
                              pq_getmsgend(&input_message);

                              exec_simple_query(query_string);

                              send_ready_for_query = true;
                        }
                        break;

                  case 'P':               /* parse */
                        {
                              const char *stmt_name;
                              const char *query_string;
                              int               numParams;
                              Oid            *paramTypes = NULL;

                              /* Set statement_timestamp() */
                              SetCurrentStatementStartTimestamp();

                              stmt_name = pq_getmsgstring(&input_message);
                              query_string = pq_getmsgstring(&input_message);
                              numParams = pq_getmsgint(&input_message, 2);
                              if (numParams > 0)
                              {
                                    int               i;

                                    paramTypes = (Oid *) palloc(numParams * sizeof(Oid));
                                    for (i = 0; i < numParams; i++)
                                          paramTypes[i] = pq_getmsgint(&input_message, 4);
                              }
                              pq_getmsgend(&input_message);

                              exec_parse_message(query_string, stmt_name,
                                                         paramTypes, numParams);
                        }
                        break;

                  case 'B':               /* bind */
                        /* Set statement_timestamp() */
                        SetCurrentStatementStartTimestamp();

                        /*
                         * this message is complex enough that it seems best to put
                         * the field extraction out-of-line
                         */
                        exec_bind_message(&input_message);
                        break;

                  case 'E':               /* execute */
                        {
                              const char *portal_name;
                              int               max_rows;

                              /* Set statement_timestamp() */
                              SetCurrentStatementStartTimestamp();

                              portal_name = pq_getmsgstring(&input_message);
                              max_rows = pq_getmsgint(&input_message, 4);
                              pq_getmsgend(&input_message);

                              exec_execute_message(portal_name, max_rows);
                        }
                        break;

                  case 'F':               /* fastpath function call */
                        /* Set statement_timestamp() */
                        SetCurrentStatementStartTimestamp();

                        /* Tell the collector what we're doing */
                        pgstat_report_activity("<FASTPATH> function call");

                        /* start an xact for this function invocation */
                        start_xact_command();

                        /*
                         * Note: we may at this point be inside an aborted
                         * transaction.  We can't throw error for that until we've
                         * finished reading the function-call message, so
                         * HandleFunctionRequest() must check for it after doing so.
                         * Be careful not to do anything that assumes we're inside a
                         * valid transaction here.
                         */

                        /* switch back to message context */
                        MemoryContextSwitchTo(MessageContext);

                        if (HandleFunctionRequest(&input_message) == EOF)
                        {
                              /* lost frontend connection during F message input */

                              /*
                               * Reset whereToSendOutput to prevent ereport from
                               * attempting to send any more messages to client.
                               */
                              if (whereToSendOutput == DestRemote)
                                    whereToSendOutput = DestNone;

                              proc_exit(0);
                        }

                        /* commit the function-invocation transaction */
                        finish_xact_command();

                        send_ready_for_query = true;
                        break;

                  case 'C':               /* close */
                        {
                              int               close_type;
                              const char *close_target;

                              close_type = pq_getmsgbyte(&input_message);
                              close_target = pq_getmsgstring(&input_message);
                              pq_getmsgend(&input_message);

                              switch (close_type)
                              {
                                    case 'S':
                                          if (close_target[0] != '\0')
                                                DropPreparedStatement(close_target, false);
                                          else
                                          {
                                                /* special-case the unnamed statement */
                                                drop_unnamed_stmt();
                                          }
                                          break;
                                    case 'P':
                                          {
                                                Portal            portal;

                                                portal = GetPortalByName(close_target);
                                                if (PortalIsValid(portal))
                                                      PortalDrop(portal, false);
                                          }
                                          break;
                                    default:
                                          ereport(ERROR,
                                                      (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                                   errmsg("invalid CLOSE message subtype %d",
                                                              close_type)));
                                          break;
                              }

                              if (whereToSendOutput == DestRemote)
                                    pq_putemptymessage('3');            /* CloseComplete */
                        }
                        break;

                  case 'D':               /* describe */
                        {
                              int               describe_type;
                              const char *describe_target;

                              /* Set statement_timestamp() (needed for xact) */
                              SetCurrentStatementStartTimestamp();

                              describe_type = pq_getmsgbyte(&input_message);
                              describe_target = pq_getmsgstring(&input_message);
                              pq_getmsgend(&input_message);

                              switch (describe_type)
                              {
                                    case 'S':
                                          exec_describe_statement_message(describe_target);
                                          break;
                                    case 'P':
                                          exec_describe_portal_message(describe_target);
                                          break;
                                    default:
                                          ereport(ERROR,
                                                      (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                                errmsg("invalid DESCRIBE message subtype %d",
                                                         describe_type)));
                                          break;
                              }
                        }
                        break;

                  case 'H':               /* flush */
                        pq_getmsgend(&input_message);
                        if (whereToSendOutput == DestRemote)
                              pq_flush();
                        break;

                  case 'S':               /* sync */
                        pq_getmsgend(&input_message);
                        finish_xact_command();
                        send_ready_for_query = true;
                        break;

                        /*
                         * 'X' means that the frontend is closing down the socket. EOF
                         * means unexpected loss of frontend connection. Either way,
                         * perform normal shutdown.
                         */
                  case 'X':
                  case EOF:

                        /*
                         * Reset whereToSendOutput to prevent ereport from attempting
                         * to send any more messages to client.
                         */
                        if (whereToSendOutput == DestRemote)
                              whereToSendOutput = DestNone;

                        /*
                         * NOTE: if you are tempted to add more code here, DON'T!
                         * Whatever you had in mind to do should be set up as an
                         * on_proc_exit or on_shmem_exit callback, instead. Otherwise
                         * it will fail to be called during other backend-shutdown
                         * scenarios.
                         */
                        proc_exit(0);

                  case 'd':               /* copy data */
                  case 'c':               /* copy done */
                  case 'f':               /* copy fail */

                        /*
                         * Accept but ignore these messages, per protocol spec; we
                         * probably got here because a COPY failed, and the frontend
                         * is still sending data.
                         */
                        break;

                  default:
                        ereport(FATAL,
                                    (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                     errmsg("invalid frontend message type %d",
                                                firstchar)));
            }
      }                                         /* end of input-reading loop */

      /* can't get here because the above loop never exits */
      Assert(false);

      return 1;                           /* keep compiler quiet */
}


/*
 * Obtain platform stack depth limit (in bytes)
 *
 * Return -1 if unlimited or not known
 */
long
get_stack_depth_rlimit(void)
{
#if defined(HAVE_GETRLIMIT) && defined(RLIMIT_STACK)
      static long val = 0;

      /* This won't change after process launch, so check just once */
      if (val == 0)
      {
            struct rlimit rlim;

            if (getrlimit(RLIMIT_STACK, &rlim) < 0)
                  val = -1;
            else if (rlim.rlim_cur == RLIM_INFINITY)
                  val = -1;
            else
                  val = rlim.rlim_cur;
      }
      return val;
#else                                     /* no getrlimit */
#if defined(WIN32) || defined(__CYGWIN__)
      /* On Windows we set the backend stack size in src/backend/Makefile */
      return WIN32_STACK_RLIMIT;
#else                                     /* not windows ... give up */
      return -1;
#endif
#endif
}


static struct rusage Save_r;
static struct timeval Save_t;

void
ResetUsage(void)
{
      getrusage(RUSAGE_SELF, &Save_r);
      gettimeofday(&Save_t, NULL);
      ResetBufferUsage();
      /* ResetTupleCount(); */
}

void
ShowUsage(const char *title)
{
      StringInfoData str;
      struct timeval user,
                        sys;
      struct timeval elapse_t;
      struct rusage r;
      char     *bufusage;

      getrusage(RUSAGE_SELF, &r);
      gettimeofday(&elapse_t, NULL);
      memcpy((char *) &user, (char *) &r.ru_utime, sizeof(user));
      memcpy((char *) &sys, (char *) &r.ru_stime, sizeof(sys));
      if (elapse_t.tv_usec < Save_t.tv_usec)
      {
            elapse_t.tv_sec--;
            elapse_t.tv_usec += 1000000;
      }
      if (r.ru_utime.tv_usec < Save_r.ru_utime.tv_usec)
      {
            r.ru_utime.tv_sec--;
            r.ru_utime.tv_usec += 1000000;
      }
      if (r.ru_stime.tv_usec < Save_r.ru_stime.tv_usec)
      {
            r.ru_stime.tv_sec--;
            r.ru_stime.tv_usec += 1000000;
      }

      /*
       * the only stats we don't show here are for memory usage -- i can't
       * figure out how to interpret the relevant fields in the rusage struct,
       * and they change names across o/s platforms, anyway. if you can figure
       * out what the entries mean, you can somehow extract resident set size,
       * shared text size, and unshared data and stack sizes.
       */
      initStringInfo(&str);

      appendStringInfo(&str, "! system usage stats:\n");
      appendStringInfo(&str,
                        "!\t%ld.%06ld elapsed %ld.%06ld user %ld.%06ld system sec\n",
                               (long) (elapse_t.tv_sec - Save_t.tv_sec),
                               (long) (elapse_t.tv_usec - Save_t.tv_usec),
                               (long) (r.ru_utime.tv_sec - Save_r.ru_utime.tv_sec),
                               (long) (r.ru_utime.tv_usec - Save_r.ru_utime.tv_usec),
                               (long) (r.ru_stime.tv_sec - Save_r.ru_stime.tv_sec),
                               (long) (r.ru_stime.tv_usec - Save_r.ru_stime.tv_usec));
      appendStringInfo(&str,
                               "!\t[%ld.%06ld user %ld.%06ld sys total]\n",
                               (long) user.tv_sec,
                               (long) user.tv_usec,
                               (long) sys.tv_sec,
                               (long) sys.tv_usec);
#if defined(HAVE_GETRUSAGE)
      appendStringInfo(&str,
                               "!\t%ld/%ld [%ld/%ld] filesystem blocks in/out\n",
                               r.ru_inblock - Save_r.ru_inblock,
      /* they only drink coffee at dec */
                               r.ru_oublock - Save_r.ru_oublock,
                               r.ru_inblock, r.ru_oublock);
      appendStringInfo(&str,
                    "!\t%ld/%ld [%ld/%ld] page faults/reclaims, %ld [%ld] swaps\n",
                               r.ru_majflt - Save_r.ru_majflt,
                               r.ru_minflt - Save_r.ru_minflt,
                               r.ru_majflt, r.ru_minflt,
                               r.ru_nswap - Save_r.ru_nswap,
                               r.ru_nswap);
      appendStringInfo(&str,
             "!\t%ld [%ld] signals rcvd, %ld/%ld [%ld/%ld] messages rcvd/sent\n",
                               r.ru_nsignals - Save_r.ru_nsignals,
                               r.ru_nsignals,
                               r.ru_msgrcv - Save_r.ru_msgrcv,
                               r.ru_msgsnd - Save_r.ru_msgsnd,
                               r.ru_msgrcv, r.ru_msgsnd);
      appendStringInfo(&str,
                   "!\t%ld/%ld [%ld/%ld] voluntary/involuntary context switches\n",
                               r.ru_nvcsw - Save_r.ru_nvcsw,
                               r.ru_nivcsw - Save_r.ru_nivcsw,
                               r.ru_nvcsw, r.ru_nivcsw);
#endif   /* HAVE_GETRUSAGE */

      bufusage = ShowBufferUsage();
      appendStringInfo(&str, "! buffer usage stats:\n%s", bufusage);
      pfree(bufusage);

      /* remove trailing newline */
      if (str.data[str.len - 1] == '\n')
            str.data[--str.len] = '\0';

      ereport(LOG,
                  (errmsg_internal("%s", title),
                   errdetail("%s", str.data)));

      pfree(str.data);
}

/*
 * on_proc_exit handler to log end of session
 */
static void
log_disconnections(int code, Datum arg)
{
      Port     *port = MyProcPort;
      long        secs;
      int               usecs;
      int               msecs;
      int               hours,
                        minutes,
                        seconds;

      TimestampDifference(port->SessionStartTime,
                                    GetCurrentTimestamp(),
                                    &secs, &usecs);
      msecs = usecs / 1000;

      hours = secs / SECS_PER_HOUR;
      secs %= SECS_PER_HOUR;
      minutes = secs / SECS_PER_MINUTE;
      seconds = secs % SECS_PER_MINUTE;

      ereport(LOG,
                  (errmsg("disconnection: session time: %d:%02d:%02d.%03d "
                              "user=%s database=%s host=%s%s%s",
                              hours, minutes, seconds, msecs,
                              port->user_name, port->database_name, port->remote_host,
                          port->remote_port[0] ? " port=" : "", port->remote_port)));
}

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