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Sourcecode: postgresql-8.4 version File versions

pg_resetxlog.c

/*-------------------------------------------------------------------------
 *
 * pg_resetxlog.c
 *      A utility to "zero out" the xlog when it's corrupt beyond recovery.
 *      Can also rebuild pg_control if needed.
 *
 * The theory of operation is fairly simple:
 *      1. Read the existing pg_control (which will include the last
 *           checkpoint record).  If it is an old format then update to
 *           current format.
 *      2. If pg_control is corrupt, attempt to intuit reasonable values,
 *           by scanning the old xlog if necessary.
 *      3. Modify pg_control to reflect a "shutdown" state with a checkpoint
 *           record at the start of xlog.
 *      4. Flush the existing xlog files and write a new segment with
 *           just a checkpoint record in it.  The new segment is positioned
 *           just past the end of the old xlog, so that existing LSNs in
 *           data pages will appear to be "in the past".
 * This is all pretty straightforward except for the intuition part of
 * step 2 ...
 *
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $PostgreSQL$
 *
 *-------------------------------------------------------------------------
 */

/*
 * We have to use postgres.h not postgres_fe.h here, because there's so much
 * backend-only stuff in the XLOG include files we need.  But we need a
 * frontend-ish environment otherwise.  Hence this ugly hack.
 */
#define FRONTEND 1

#include "postgres.h"

#include <dirent.h>
#include <fcntl.h>
#include <locale.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
#ifdef HAVE_GETOPT_H
#include <getopt.h>
#endif

#include "access/transam.h"
#include "access/tuptoaster.h"
#include "access/multixact.h"
#include "access/xlog_internal.h"
#include "catalog/catversion.h"
#include "catalog/pg_control.h"

extern int  optind;
extern char *optarg;


static ControlFileData ControlFile;       /* pg_control values */
static uint32 newXlogId,
                  newXlogSeg;             /* ID/Segment of new XLOG segment */
static bool guessed = false;  /* T if we had to guess at any values */
static const char *progname;

static bool ReadControlFile(void);
static void GuessControlValues(void);
static void PrintControlValues(bool guessed);
static void RewriteControlFile(void);
static void FindEndOfXLOG(void);
static void KillExistingXLOG(void);
static void WriteEmptyXLOG(void);
static void usage(void);


int
main(int argc, char *argv[])
{
      int               c;
      bool        force = false;
      bool        noupdate = false;
      uint32            set_xid_epoch = (uint32) -1;
      TransactionId set_xid = 0;
      Oid               set_oid = 0;
      MultiXactId set_mxid = 0;
      MultiXactOffset set_mxoff = (MultiXactOffset) -1;
      uint32            minXlogTli = 0,
                        minXlogId = 0,
                        minXlogSeg = 0;
      char     *endptr;
      char     *endptr2;
      char     *endptr3;
      char     *DataDir;
      int               fd;
      char        path[MAXPGPATH];

      set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_resetxlog"));

      progname = get_progname(argv[0]);

      if (argc > 1)
      {
            if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-?") == 0)
            {
                  usage();
                  exit(0);
            }
            if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
            {
                  puts("pg_resetxlog (PostgreSQL) " PG_VERSION);
                  exit(0);
            }
      }


      while ((c = getopt(argc, argv, "fl:m:no:O:x:e:")) != -1)
      {
            switch (c)
            {
                  case 'f':
                        force = true;
                        break;

                  case 'n':
                        noupdate = true;
                        break;

                  case 'e':
                        set_xid_epoch = strtoul(optarg, &endptr, 0);
                        if (endptr == optarg || *endptr != '\0')
                        {
                              fprintf(stderr, _("%s: invalid argument for option -e\n"), progname);
                              fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                              exit(1);
                        }
                        if (set_xid_epoch == -1)
                        {
                              fprintf(stderr, _("%s: transaction ID epoch (-e) must not be -1\n"), progname);
                              exit(1);
                        }
                        break;

                  case 'x':
                        set_xid = strtoul(optarg, &endptr, 0);
                        if (endptr == optarg || *endptr != '\0')
                        {
                              fprintf(stderr, _("%s: invalid argument for option -x\n"), progname);
                              fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                              exit(1);
                        }
                        if (set_xid == 0)
                        {
                              fprintf(stderr, _("%s: transaction ID (-x) must not be 0\n"), progname);
                              exit(1);
                        }
                        break;

                  case 'o':
                        set_oid = strtoul(optarg, &endptr, 0);
                        if (endptr == optarg || *endptr != '\0')
                        {
                              fprintf(stderr, _("%s: invalid argument for option -o\n"), progname);
                              fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                              exit(1);
                        }
                        if (set_oid == 0)
                        {
                              fprintf(stderr, _("%s: OID (-o) must not be 0\n"), progname);
                              exit(1);
                        }
                        break;

                  case 'm':
                        set_mxid = strtoul(optarg, &endptr, 0);
                        if (endptr == optarg || *endptr != '\0')
                        {
                              fprintf(stderr, _("%s: invalid argument for option -m\n"), progname);
                              fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                              exit(1);
                        }
                        if (set_mxid == 0)
                        {
                              fprintf(stderr, _("%s: multitransaction ID (-m) must not be 0\n"), progname);
                              exit(1);
                        }
                        break;

                  case 'O':
                        set_mxoff = strtoul(optarg, &endptr, 0);
                        if (endptr == optarg || *endptr != '\0')
                        {
                              fprintf(stderr, _("%s: invalid argument for option -O\n"), progname);
                              fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                              exit(1);
                        }
                        if (set_mxoff == -1)
                        {
                              fprintf(stderr, _("%s: multitransaction offset (-O) must not be -1\n"), progname);
                              exit(1);
                        }
                        break;

                  case 'l':
                        minXlogTli = strtoul(optarg, &endptr, 0);
                        if (endptr == optarg || *endptr != ',')
                        {
                              fprintf(stderr, _("%s: invalid argument for option -l\n"), progname);
                              fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                              exit(1);
                        }
                        minXlogId = strtoul(endptr + 1, &endptr2, 0);
                        if (endptr2 == endptr + 1 || *endptr2 != ',')
                        {
                              fprintf(stderr, _("%s: invalid argument for option -l\n"), progname);
                              fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                              exit(1);
                        }
                        minXlogSeg = strtoul(endptr2 + 1, &endptr3, 0);
                        if (endptr3 == endptr2 + 1 || *endptr3 != '\0')
                        {
                              fprintf(stderr, _("%s: invalid argument for option -l\n"), progname);
                              fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                              exit(1);
                        }
                        break;

                  default:
                        fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                        exit(1);
            }
      }

      if (optind == argc)
      {
            fprintf(stderr, _("%s: no data directory specified\n"), progname);
            fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
            exit(1);
      }

      /*
       * Don't allow pg_resetxlog to be run as root, to avoid overwriting the
       * ownership of files in the data directory. We need only check for root
       * -- any other user won't have sufficient permissions to modify files in
       * the data directory.
       */
#ifndef WIN32
      if (geteuid() == 0)
      {
            fprintf(stderr, _("%s: cannot be executed by \"root\"\n"),
                        progname);
            fprintf(stderr, _("You must run %s as the PostgreSQL superuser.\n"),
                        progname);
            exit(1);
      }
#endif

      DataDir = argv[optind];

      if (chdir(DataDir) < 0)
      {
            fprintf(stderr, _("%s: could not change directory to \"%s\": %s\n"),
                        progname, DataDir, strerror(errno));
            exit(1);
      }

      /*
       * Check for a postmaster lock file --- if there is one, refuse to
       * proceed, on grounds we might be interfering with a live installation.
       */
      snprintf(path, MAXPGPATH, "%s/postmaster.pid", DataDir);

      if ((fd = open(path, O_RDONLY, 0)) < 0)
      {
            if (errno != ENOENT)
            {
                  fprintf(stderr, _("%s: could not open file \"%s\" for reading: %s\n"), progname, path, strerror(errno));
                  exit(1);
            }
      }
      else
      {
            fprintf(stderr, _("%s: lock file \"%s\" exists\n"
                                      "Is a server running?  If not, delete the lock file and try again.\n"),
                        progname, path);
            exit(1);
      }

      /*
       * Attempt to read the existing pg_control file
       */
      if (!ReadControlFile())
            GuessControlValues();

      /*
       * Also look at existing segment files to set up newXlogId/newXlogSeg
       */
      FindEndOfXLOG();

      /*
       * Adjust fields if required by switches.  (Do this now so that printout,
       * if any, includes these values.)
       */
      if (set_xid_epoch != -1)
            ControlFile.checkPointCopy.nextXidEpoch = set_xid_epoch;

      if (set_xid != 0)
            ControlFile.checkPointCopy.nextXid = set_xid;

      if (set_oid != 0)
            ControlFile.checkPointCopy.nextOid = set_oid;

      if (set_mxid != 0)
            ControlFile.checkPointCopy.nextMulti = set_mxid;

      if (set_mxoff != -1)
            ControlFile.checkPointCopy.nextMultiOffset = set_mxoff;

      if (minXlogTli > ControlFile.checkPointCopy.ThisTimeLineID)
            ControlFile.checkPointCopy.ThisTimeLineID = minXlogTli;

      if (minXlogId > newXlogId ||
            (minXlogId == newXlogId &&
             minXlogSeg > newXlogSeg))
      {
            newXlogId = minXlogId;
            newXlogSeg = minXlogSeg;
      }

      /*
       * If we had to guess anything, and -f was not given, just print the
       * guessed values and exit.  Also print if -n is given.
       */
      if ((guessed && !force) || noupdate)
      {
            PrintControlValues(guessed);
            if (!noupdate)
            {
                  printf(_("\nIf these values seem acceptable, use -f to force reset.\n"));
                  exit(1);
            }
            else
                  exit(0);
      }

      /*
       * Don't reset from a dirty pg_control without -f, either.
       */
      if (ControlFile.state != DB_SHUTDOWNED && !force)
      {
            printf(_("The database server was not shut down cleanly.\n"
                     "Resetting the transaction log might cause data to be lost.\n"
                         "If you want to proceed anyway, use -f to force reset.\n"));
            exit(1);
      }

      /*
       * Else, do the dirty deed.
       */
      RewriteControlFile();
      KillExistingXLOG();
      WriteEmptyXLOG();

      printf(_("Transaction log reset\n"));
      return 0;
}


/*
 * Try to read the existing pg_control file.
 *
 * This routine is also responsible for updating old pg_control versions
 * to the current format.  (Currently we don't do anything of the sort.)
 */
static bool
ReadControlFile(void)
{
      int               fd;
      int               len;
      char     *buffer;
      pg_crc32    crc;

      if ((fd = open(XLOG_CONTROL_FILE, O_RDONLY | PG_BINARY, 0)) < 0)
      {
            /*
             * If pg_control is not there at all, or we can't read it, the odds
             * are we've been handed a bad DataDir path, so give up. User can do
             * "touch pg_control" to force us to proceed.
             */
            fprintf(stderr, _("%s: could not open file \"%s\" for reading: %s\n"),
                        progname, XLOG_CONTROL_FILE, strerror(errno));
            if (errno == ENOENT)
                  fprintf(stderr, _("If you are sure the data directory path is correct, execute\n"
                                            "  touch %s\n"
                                            "and try again.\n"),
                              XLOG_CONTROL_FILE);
            exit(1);
      }

      /* Use malloc to ensure we have a maxaligned buffer */
      buffer = (char *) malloc(PG_CONTROL_SIZE);

      len = read(fd, buffer, PG_CONTROL_SIZE);
      if (len < 0)
      {
            fprintf(stderr, _("%s: could not read file \"%s\": %s\n"),
                        progname, XLOG_CONTROL_FILE, strerror(errno));
            exit(1);
      }
      close(fd);

      if (len >= sizeof(ControlFileData) &&
        ((ControlFileData *) buffer)->pg_control_version == PG_CONTROL_VERSION)
      {
            /* Check the CRC. */
            INIT_CRC32(crc);
            COMP_CRC32(crc,
                           buffer,
                           offsetof(ControlFileData, crc));
            FIN_CRC32(crc);

            if (EQ_CRC32(crc, ((ControlFileData *) buffer)->crc))
            {
                  /* Valid data... */
                  memcpy(&ControlFile, buffer, sizeof(ControlFile));
                  return true;
            }

            fprintf(stderr, _("%s: pg_control exists but has invalid CRC; proceed with caution\n"),
                        progname);
            /* We will use the data anyway, but treat it as guessed. */
            memcpy(&ControlFile, buffer, sizeof(ControlFile));
            guessed = true;
            return true;
      }

      /* Looks like it's a mess. */
      fprintf(stderr, _("%s: pg_control exists but is broken or unknown version; ignoring it\n"),
                  progname);
      return false;
}


/*
 * Guess at pg_control values when we can't read the old ones.
 */
static void
GuessControlValues(void)
{
      uint64            sysidentifier;
      struct timeval tv;

      /*
       * Set up a completely default set of pg_control values.
       */
      guessed = true;
      memset(&ControlFile, 0, sizeof(ControlFile));

      ControlFile.pg_control_version = PG_CONTROL_VERSION;
      ControlFile.catalog_version_no = CATALOG_VERSION_NO;

      /*
       * Create a new unique installation identifier, since we can no longer use
       * any old XLOG records.  See notes in xlog.c about the algorithm.
       */
      gettimeofday(&tv, NULL);
      sysidentifier = ((uint64) tv.tv_sec) << 32;
      sysidentifier |= (uint32) (tv.tv_sec | tv.tv_usec);

      ControlFile.system_identifier = sysidentifier;

      ControlFile.checkPointCopy.redo.xlogid = 0;
      ControlFile.checkPointCopy.redo.xrecoff = SizeOfXLogLongPHD;
      ControlFile.checkPointCopy.ThisTimeLineID = 1;
      ControlFile.checkPointCopy.nextXidEpoch = 0;
      ControlFile.checkPointCopy.nextXid = (TransactionId) 514;   /* XXX */
      ControlFile.checkPointCopy.nextOid = FirstBootstrapObjectId;
      ControlFile.checkPointCopy.nextMulti = FirstMultiXactId;
      ControlFile.checkPointCopy.nextMultiOffset = 0;
      ControlFile.checkPointCopy.time = (pg_time_t) time(NULL);

      ControlFile.state = DB_SHUTDOWNED;
      ControlFile.time = (pg_time_t) time(NULL);
      ControlFile.checkPoint = ControlFile.checkPointCopy.redo;

      ControlFile.maxAlign = MAXIMUM_ALIGNOF;
      ControlFile.floatFormat = FLOATFORMAT_VALUE;
      ControlFile.blcksz = BLCKSZ;
      ControlFile.relseg_size = RELSEG_SIZE;
      ControlFile.xlog_blcksz = XLOG_BLCKSZ;
      ControlFile.xlog_seg_size = XLOG_SEG_SIZE;
      ControlFile.nameDataLen = NAMEDATALEN;
      ControlFile.indexMaxKeys = INDEX_MAX_KEYS;
      ControlFile.toast_max_chunk_size = TOAST_MAX_CHUNK_SIZE;
#ifdef HAVE_INT64_TIMESTAMP
      ControlFile.enableIntTimes = true;
#else
      ControlFile.enableIntTimes = false;
#endif
      ControlFile.float4ByVal = FLOAT4PASSBYVAL;
      ControlFile.float8ByVal = FLOAT8PASSBYVAL;

      /*
       * XXX eventually, should try to grovel through old XLOG to develop more
       * accurate values for TimeLineID, nextXID, etc.
       */
}


/*
 * Print the guessed pg_control values when we had to guess.
 *
 * NB: this display should be just those fields that will not be
 * reset by RewriteControlFile().
 */
static void
PrintControlValues(bool guessed)
{
      char        sysident_str[32];

      if (guessed)
            printf(_("Guessed pg_control values:\n\n"));
      else
            printf(_("pg_control values:\n\n"));

      /*
       * Format system_identifier separately to keep platform-dependent format
       * code out of the translatable message string.
       */
      snprintf(sysident_str, sizeof(sysident_str), UINT64_FORMAT,
                   ControlFile.system_identifier);

      printf(_("First log file ID after reset:        %u\n"),
               newXlogId);
      printf(_("First log file segment after reset:   %u\n"),
               newXlogSeg);
      printf(_("pg_control version number:            %u\n"),
               ControlFile.pg_control_version);
      printf(_("Catalog version number:               %u\n"),
               ControlFile.catalog_version_no);
      printf(_("Database system identifier:           %s\n"),
               sysident_str);
      printf(_("Latest checkpoint's TimeLineID:       %u\n"),
               ControlFile.checkPointCopy.ThisTimeLineID);
      printf(_("Latest checkpoint's NextXID:          %u/%u\n"),
               ControlFile.checkPointCopy.nextXidEpoch,
               ControlFile.checkPointCopy.nextXid);
      printf(_("Latest checkpoint's NextOID:          %u\n"),
               ControlFile.checkPointCopy.nextOid);
      printf(_("Latest checkpoint's NextMultiXactId:  %u\n"),
               ControlFile.checkPointCopy.nextMulti);
      printf(_("Latest checkpoint's NextMultiOffset:  %u\n"),
               ControlFile.checkPointCopy.nextMultiOffset);
      printf(_("Maximum data alignment:               %u\n"),
               ControlFile.maxAlign);
      /* we don't print floatFormat since can't say much useful about it */
      printf(_("Database block size:                  %u\n"),
               ControlFile.blcksz);
      printf(_("Blocks per segment of large relation: %u\n"),
               ControlFile.relseg_size);
      printf(_("WAL block size:                       %u\n"),
               ControlFile.xlog_blcksz);
      printf(_("Bytes per WAL segment:                %u\n"),
               ControlFile.xlog_seg_size);
      printf(_("Maximum length of identifiers:        %u\n"),
               ControlFile.nameDataLen);
      printf(_("Maximum columns in an index:          %u\n"),
               ControlFile.indexMaxKeys);
      printf(_("Maximum size of a TOAST chunk:        %u\n"),
               ControlFile.toast_max_chunk_size);
      printf(_("Date/time type storage:               %s\n"),
               (ControlFile.enableIntTimes ? _("64-bit integers") : _("floating-point numbers")));
      printf(_("Float4 argument passing:              %s\n"),
               (ControlFile.float4ByVal ? _("by value") : _("by reference")));
      printf(_("Float8 argument passing:              %s\n"),
               (ControlFile.float8ByVal ? _("by value") : _("by reference")));
}


/*
 * Write out the new pg_control file.
 */
static void
RewriteControlFile(void)
{
      int               fd;
      char        buffer[PG_CONTROL_SIZE];            /* need not be aligned */

      /*
       * Adjust fields as needed to force an empty XLOG starting at
       * newXlogId/newXlogSeg.
       */
      ControlFile.checkPointCopy.redo.xlogid = newXlogId;
      ControlFile.checkPointCopy.redo.xrecoff =
            newXlogSeg * XLogSegSize + SizeOfXLogLongPHD;
      ControlFile.checkPointCopy.time = (pg_time_t) time(NULL);

      ControlFile.state = DB_SHUTDOWNED;
      ControlFile.time = (pg_time_t) time(NULL);
      ControlFile.checkPoint = ControlFile.checkPointCopy.redo;
      ControlFile.prevCheckPoint.xlogid = 0;
      ControlFile.prevCheckPoint.xrecoff = 0;
      ControlFile.minRecoveryPoint.xlogid = 0;
      ControlFile.minRecoveryPoint.xrecoff = 0;

      /* Now we can force the recorded xlog seg size to the right thing. */
      ControlFile.xlog_seg_size = XLogSegSize;

      /* Contents are protected with a CRC */
      INIT_CRC32(ControlFile.crc);
      COMP_CRC32(ControlFile.crc,
                     (char *) &ControlFile,
                     offsetof(ControlFileData, crc));
      FIN_CRC32(ControlFile.crc);

      /*
       * We write out PG_CONTROL_SIZE bytes into pg_control, zero-padding the
       * excess over sizeof(ControlFileData).  This reduces the odds of
       * premature-EOF errors when reading pg_control.  We'll still fail when we
       * check the contents of the file, but hopefully with a more specific
       * error than "couldn't read pg_control".
       */
      if (sizeof(ControlFileData) > PG_CONTROL_SIZE)
      {
            fprintf(stderr,
                        _("%s: internal error -- sizeof(ControlFileData) is too large ... fix PG_CONTROL_SIZE\n"),
                        progname);
            exit(1);
      }

      memset(buffer, 0, PG_CONTROL_SIZE);
      memcpy(buffer, &ControlFile, sizeof(ControlFileData));

      unlink(XLOG_CONTROL_FILE);

      fd = open(XLOG_CONTROL_FILE,
                    O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
                    S_IRUSR | S_IWUSR);
      if (fd < 0)
      {
            fprintf(stderr, _("%s: could not create pg_control file: %s\n"),
                        progname, strerror(errno));
            exit(1);
      }

      errno = 0;
      if (write(fd, buffer, PG_CONTROL_SIZE) != PG_CONTROL_SIZE)
      {
            /* if write didn't set errno, assume problem is no disk space */
            if (errno == 0)
                  errno = ENOSPC;
            fprintf(stderr, _("%s: could not write pg_control file: %s\n"),
                        progname, strerror(errno));
            exit(1);
      }

      if (fsync(fd) != 0)
      {
            fprintf(stderr, _("%s: fsync error: %s\n"), progname, strerror(errno));
            exit(1);
      }

      close(fd);
}


/*
 * Scan existing XLOG files and determine the highest existing WAL address
 *
 * On entry, ControlFile.checkPointCopy.redo and ControlFile.xlog_seg_size
 * are assumed valid (note that we allow the old xlog seg size to differ
 * from what we're using).  On exit, newXlogId and newXlogSeg are set to
 * suitable values for the beginning of replacement WAL (in our seg size).
 */
static void
FindEndOfXLOG(void)
{
      DIR            *xldir;
      struct dirent *xlde;

      /*
       * Initialize the max() computation using the last checkpoint address from
       * old pg_control.      Note that for the moment we are working with segment
       * numbering according to the old xlog seg size.
       */
      newXlogId = ControlFile.checkPointCopy.redo.xlogid;
      newXlogSeg = ControlFile.checkPointCopy.redo.xrecoff / ControlFile.xlog_seg_size;

      /*
       * Scan the pg_xlog directory to find existing WAL segment files. We
       * assume any present have been used; in most scenarios this should be
       * conservative, because of xlog.c's attempts to pre-create files.
       */
      xldir = opendir(XLOGDIR);
      if (xldir == NULL)
      {
            fprintf(stderr, _("%s: could not open directory \"%s\": %s\n"),
                        progname, XLOGDIR, strerror(errno));
            exit(1);
      }

      errno = 0;
      while ((xlde = readdir(xldir)) != NULL)
      {
            if (strlen(xlde->d_name) == 24 &&
                  strspn(xlde->d_name, "0123456789ABCDEF") == 24)
            {
                  unsigned int tli,
                                    log,
                                    seg;

                  sscanf(xlde->d_name, "%08X%08X%08X", &tli, &log, &seg);

                  /*
                   * Note: we take the max of all files found, regardless of their
                   * timelines.  Another possibility would be to ignore files of
                   * timelines other than the target TLI, but this seems safer.
                   * Better too large a result than too small...
                   */
                  if (log > newXlogId ||
                        (log == newXlogId && seg > newXlogSeg))
                  {
                        newXlogId = log;
                        newXlogSeg = seg;
                  }
            }
            errno = 0;
      }
#ifdef WIN32

      /*
       * This fix is in mingw cvs (runtime/mingwex/dirent.c rev 1.4), but not in
       * released version
       */
      if (GetLastError() == ERROR_NO_MORE_FILES)
            errno = 0;
#endif

      if (errno)
      {
            fprintf(stderr, _("%s: could not read from directory \"%s\": %s\n"),
                        progname, XLOGDIR, strerror(errno));
            exit(1);
      }
      closedir(xldir);

      /*
       * Finally, convert to new xlog seg size, and advance by one to ensure we
       * are in virgin territory.
       */
      newXlogSeg *= ControlFile.xlog_seg_size;
      newXlogSeg = (newXlogSeg + XLogSegSize - 1) / XLogSegSize;

      /* be sure we wrap around correctly at end of a logfile */
      NextLogSeg(newXlogId, newXlogSeg);
}


/*
 * Remove existing XLOG files
 */
static void
KillExistingXLOG(void)
{
      DIR            *xldir;
      struct dirent *xlde;
      char        path[MAXPGPATH];

      xldir = opendir(XLOGDIR);
      if (xldir == NULL)
      {
            fprintf(stderr, _("%s: could not open directory \"%s\": %s\n"),
                        progname, XLOGDIR, strerror(errno));
            exit(1);
      }

      errno = 0;
      while ((xlde = readdir(xldir)) != NULL)
      {
            if (strlen(xlde->d_name) == 24 &&
                  strspn(xlde->d_name, "0123456789ABCDEF") == 24)
            {
                  snprintf(path, MAXPGPATH, "%s/%s", XLOGDIR, xlde->d_name);
                  if (unlink(path) < 0)
                  {
                        fprintf(stderr, _("%s: could not delete file \"%s\": %s\n"),
                                    progname, path, strerror(errno));
                        exit(1);
                  }
            }
            errno = 0;
      }
#ifdef WIN32

      /*
       * This fix is in mingw cvs (runtime/mingwex/dirent.c rev 1.4), but not in
       * released version
       */
      if (GetLastError() == ERROR_NO_MORE_FILES)
            errno = 0;
#endif

      if (errno)
      {
            fprintf(stderr, _("%s: could not read from directory \"%s\": %s\n"),
                        progname, XLOGDIR, strerror(errno));
            exit(1);
      }
      closedir(xldir);
}


/*
 * Write an empty XLOG file, containing only the checkpoint record
 * already set up in ControlFile.
 */
static void
WriteEmptyXLOG(void)
{
      char     *buffer;
      XLogPageHeader page;
      XLogLongPageHeader longpage;
      XLogRecord *record;
      pg_crc32    crc;
      char        path[MAXPGPATH];
      int               fd;
      int               nbytes;

      /* Use malloc() to ensure buffer is MAXALIGNED */
      buffer = (char *) malloc(XLOG_BLCKSZ);
      page = (XLogPageHeader) buffer;
      memset(buffer, 0, XLOG_BLCKSZ);

      /* Set up the XLOG page header */
      page->xlp_magic = XLOG_PAGE_MAGIC;
      page->xlp_info = XLP_LONG_HEADER;
      page->xlp_tli = ControlFile.checkPointCopy.ThisTimeLineID;
      page->xlp_pageaddr.xlogid =
            ControlFile.checkPointCopy.redo.xlogid;
      page->xlp_pageaddr.xrecoff =
            ControlFile.checkPointCopy.redo.xrecoff - SizeOfXLogLongPHD;
      longpage = (XLogLongPageHeader) page;
      longpage->xlp_sysid = ControlFile.system_identifier;
      longpage->xlp_seg_size = XLogSegSize;
      longpage->xlp_xlog_blcksz = XLOG_BLCKSZ;

      /* Insert the initial checkpoint record */
      record = (XLogRecord *) ((char *) page + SizeOfXLogLongPHD);
      record->xl_prev.xlogid = 0;
      record->xl_prev.xrecoff = 0;
      record->xl_xid = InvalidTransactionId;
      record->xl_tot_len = SizeOfXLogRecord + sizeof(CheckPoint);
      record->xl_len = sizeof(CheckPoint);
      record->xl_info = XLOG_CHECKPOINT_SHUTDOWN;
      record->xl_rmid = RM_XLOG_ID;
      memcpy(XLogRecGetData(record), &ControlFile.checkPointCopy,
               sizeof(CheckPoint));

      INIT_CRC32(crc);
      COMP_CRC32(crc, &ControlFile.checkPointCopy, sizeof(CheckPoint));
      COMP_CRC32(crc, (char *) record + sizeof(pg_crc32),
                     SizeOfXLogRecord - sizeof(pg_crc32));
      FIN_CRC32(crc);
      record->xl_crc = crc;

      /* Write the first page */
      XLogFilePath(path, ControlFile.checkPointCopy.ThisTimeLineID,
                         newXlogId, newXlogSeg);

      unlink(path);

      fd = open(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
                    S_IRUSR | S_IWUSR);
      if (fd < 0)
      {
            fprintf(stderr, _("%s: could not open file \"%s\": %s\n"),
                        progname, path, strerror(errno));
            exit(1);
      }

      errno = 0;
      if (write(fd, buffer, XLOG_BLCKSZ) != XLOG_BLCKSZ)
      {
            /* if write didn't set errno, assume problem is no disk space */
            if (errno == 0)
                  errno = ENOSPC;
            fprintf(stderr, _("%s: could not write file \"%s\": %s\n"),
                        progname, path, strerror(errno));
            exit(1);
      }

      /* Fill the rest of the file with zeroes */
      memset(buffer, 0, XLOG_BLCKSZ);
      for (nbytes = XLOG_BLCKSZ; nbytes < XLogSegSize; nbytes += XLOG_BLCKSZ)
      {
            errno = 0;
            if (write(fd, buffer, XLOG_BLCKSZ) != XLOG_BLCKSZ)
            {
                  if (errno == 0)
                        errno = ENOSPC;
                  fprintf(stderr, _("%s: could not write file \"%s\": %s\n"),
                              progname, path, strerror(errno));
                  exit(1);
            }
      }

      if (fsync(fd) != 0)
      {
            fprintf(stderr, _("%s: fsync error: %s\n"), progname, strerror(errno));
            exit(1);
      }

      close(fd);
}


static void
usage(void)
{
      printf(_("%s resets the PostgreSQL transaction log.\n\n"), progname);
      printf(_("Usage:\n  %s [OPTION]... DATADIR\n\n"), progname);
      printf(_("Options:\n"));
      printf(_("  -e XIDEPOCH     set next transaction ID epoch\n"));
      printf(_("  -f              force update to be done\n"));
      printf(_("  -l TLI,FILE,SEG force minimum WAL starting location for new transaction log\n"));
      printf(_("  -m XID          set next multitransaction ID\n"));
      printf(_("  -n              no update, just show extracted control values (for testing)\n"));
      printf(_("  -o OID          set next OID\n"));
      printf(_("  -O OFFSET       set next multitransaction offset\n"));
      printf(_("  -x XID          set next transaction ID\n"));
      printf(_("  --help          show this help, then exit\n"));
      printf(_("  --version       output version information, then exit\n"));
      printf(_("\nReport bugs to <pgsql-bugs@postgresql.org>.\n"));
}

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