pg_resetxlog.c

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/*-------------------------------------------------------------------------
 *
 * 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) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/bin/pg_resetxlog/pg_resetxlog.c
 *
 *-------------------------------------------------------------------------
 */

/*
 * 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"
#include "common/fe_memutils.h"

extern int  optind;
extern char *optarg;


static ControlFileData ControlFile;     /* pg_control values */
static XLogSegNo newXlogSegNo;  /* 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 KillExistingArchiveStatus(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;
    MultiXactId set_oldestmxid = 0;
    MultiXactOffset set_mxoff = (MultiXactOffset) -1;
    uint32      minXlogTli = 0;
    XLogSegNo   minXlogSegNo = 0;
    char       *endptr;
    char       *endptr2;
    char       *DataDir;
    int         fd;

    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 != ',')
                {
                    fprintf(stderr, _("%s: invalid argument for option -m\n"), progname);
                    fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                    exit(1);
                }

                set_oldestmxid = strtoul(endptr + 1, &endptr2, 0);
                if (endptr2 == endptr + 1 || *endptr2 != '\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);
                }
                /*
                 * XXX It'd be nice to have more sanity checks here, e.g. so
                 * that oldest is not wrapped around w.r.t. nextMulti.
                 */
                if (set_oldestmxid == 0)
                {
                    fprintf(stderr, _("%s: oldest 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':
                if (strspn(optarg, "01234567890ABCDEFabcdef") != 24)
                {
                    fprintf(stderr, _("%s: invalid argument for option -l\n"), progname);
                    fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
                    exit(1);
                }
                XLogFromFileName(optarg, &minXlogTli, &minXlogSegNo);
                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.
     */
    if ((fd = open("postmaster.pid", O_RDONLY, 0)) < 0)
    {
        if (errno != ENOENT)
        {
            fprintf(stderr, _("%s: could not open file \"%s\" for reading: %s\n"),
                    progname, "postmaster.pid", 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, "postmaster.pid");
        exit(1);
    }

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

    /*
     * Also look at existing segment files to set up newXlogSegNo
     */
    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;

        /*
         * For the moment, just set oldestXid to a value that will force
         * immediate autovacuum-for-wraparound.  It's not clear whether adding
         * user control of this is useful, so let's just do something that's
         * reasonably safe.  The magic constant here corresponds to the
         * maximum allowed value of autovacuum_freeze_max_age.
         */
        ControlFile.checkPointCopy.oldestXid = set_xid - 2000000000;
        if (ControlFile.checkPointCopy.oldestXid < FirstNormalTransactionId)
            ControlFile.checkPointCopy.oldestXid += FirstNormalTransactionId;
        ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
    }

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

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

        ControlFile.checkPointCopy.oldestMulti = set_oldestmxid;
        if (ControlFile.checkPointCopy.oldestMulti < FirstMultiXactId)
            ControlFile.checkPointCopy.oldestMulti += FirstMultiXactId;
        ControlFile.checkPointCopy.oldestMultiDB = InvalidOid;
    }

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

    if (minXlogTli > ControlFile.checkPointCopy.ThisTimeLineID)
    {
        ControlFile.checkPointCopy.ThisTimeLineID = minXlogTli;
        ControlFile.checkPointCopy.PrevTimeLineID = minXlogTli;
    }

    if (minXlogSegNo > newXlogSegNo)
        newXlogSegNo = minXlogSegNo;

    /*
     * 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();
    KillExistingArchiveStatus();
    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 *) pg_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 = SizeOfXLogLongPHD;
    ControlFile.checkPointCopy.ThisTimeLineID = 1;
    ControlFile.checkPointCopy.PrevTimeLineID = 1;
    ControlFile.checkPointCopy.fullPageWrites = false;
    ControlFile.checkPointCopy.nextXidEpoch = 0;
    ControlFile.checkPointCopy.nextXid = FirstNormalTransactionId;
    ControlFile.checkPointCopy.nextOid = FirstBootstrapObjectId;
    ControlFile.checkPointCopy.nextMulti = FirstMultiXactId;
    ControlFile.checkPointCopy.nextMultiOffset = 0;
    ControlFile.checkPointCopy.oldestXid = FirstNormalTransactionId;
    ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
    ControlFile.checkPointCopy.oldestMulti = FirstMultiXactId;
    ControlFile.checkPointCopy.oldestMultiDB = InvalidOid;
    ControlFile.checkPointCopy.time = (pg_time_t) time(NULL);
    ControlFile.checkPointCopy.oldestActiveXid = InvalidTransactionId;

    ControlFile.state = DB_SHUTDOWNED;
    ControlFile.time = (pg_time_t) time(NULL);
    ControlFile.checkPoint = ControlFile.checkPointCopy.redo;
    ControlFile.unloggedLSN = 1;

    /* minRecoveryPoint, backupStartPoint and backupEndPoint can be left zero */

    ControlFile.wal_level = WAL_LEVEL_MINIMAL;
    ControlFile.MaxConnections = 100;
    ControlFile.max_prepared_xacts = 0;
    ControlFile.max_locks_per_xact = 64;

    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];
    char        fname[MAXFNAMELEN];

    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);

    XLogFileName(fname, ControlFile.checkPointCopy.ThisTimeLineID, newXlogSegNo);

    printf(_("First log segment after reset:        %s\n"),
           fname);
    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 full_page_writes: %s\n"),
           ControlFile.checkPointCopy.fullPageWrites ? _("on") : _("off"));
    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(_("Latest checkpoint's oldestXID:        %u\n"),
           ControlFile.checkPointCopy.oldestXid);
    printf(_("Latest checkpoint's oldestXID's DB:   %u\n"),
           ControlFile.checkPointCopy.oldestXidDB);
    printf(_("Latest checkpoint's oldestActiveXID:  %u\n"),
           ControlFile.checkPointCopy.oldestActiveXid);
    printf(_("Latest checkpoint's oldestMultiXid:   %u\n"),
           ControlFile.checkPointCopy.oldestMulti);
    printf(_("Latest checkpoint's oldestMulti's DB: %u\n"),
           ControlFile.checkPointCopy.oldestMultiDB);
    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")));
    printf(_("Data page checksum version:           %u\n"),
           ControlFile.data_checksum_version);
}


/*
 * 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
     * newXlogSegNo.
     */
    XLogSegNoOffsetToRecPtr(newXlogSegNo, SizeOfXLogLongPHD,
                            ControlFile.checkPointCopy.redo);
    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 = 0;
    ControlFile.minRecoveryPoint = 0;
    ControlFile.minRecoveryPointTLI = 0;
    ControlFile.backupStartPoint = 0;
    ControlFile.backupEndPoint = 0;
    ControlFile.backupEndRequired = false;

    /*
     * Force the defaults for max_* settings. The values don't really matter
     * as long as wal_level='minimal'; the postmaster will reset these fields
     * anyway at startup.
     */
    ControlFile.wal_level = WAL_LEVEL_MINIMAL;
    ControlFile.MaxConnections = 100;
    ControlFile.max_prepared_xacts = 0;
    ControlFile.max_locks_per_xact = 64;

    /* 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;
    uint64      segs_per_xlogid;
    uint64      xlogbytepos;

    /*
     * 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.
     */
    segs_per_xlogid = (UINT64CONST(0x0000000100000000) / ControlFile.xlog_seg_size);
    newXlogSegNo = ControlFile.checkPointCopy.redo / 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;
            XLogSegNo   segno;

            sscanf(xlde->d_name, "%08X%08X%08X", &tli, &log, &seg);
            segno = ((uint64) log) * segs_per_xlogid + 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 (segno > newXlogSegNo)
                newXlogSegNo = segno;
        }
        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.
     */
    xlogbytepos = newXlogSegNo * ControlFile.xlog_seg_size;
    newXlogSegNo = (xlogbytepos + XLogSegSize - 1) / XLogSegSize;
    newXlogSegNo++;
}


/*
 * 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);
}


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

#define ARCHSTATDIR XLOGDIR "/archive_status"

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

    errno = 0;
    while ((xlde = readdir(xldir)) != NULL)
    {
        if (strspn(xlde->d_name, "0123456789ABCDEF") == 24 &&
            (strcmp(xlde->d_name + 24, ".ready") == 0 ||
             strcmp(xlde->d_name + 24, ".done") == 0))
        {
            snprintf(path, MAXPGPATH, "%s/%s", ARCHSTATDIR, 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, ARCHSTATDIR, 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 *) pg_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 = ControlFile.checkPointCopy.redo - 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 = 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, offsetof(XLogRecord, xl_crc));
    FIN_CRC32(crc);
    record->xl_crc = crc;

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

    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 XLOGFILE      force minimum WAL starting location for new transaction log\n"));
    printf(_("  -m XID,OLDEST    set next multitransaction ID and oldest value\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(_("  -V, --version    output version information, then exit\n"));
    printf(_("  -x XID           set next transaction ID\n"));
    printf(_("  -?, --help       show this help, then exit\n"));
    printf(_("\nReport bugs to <[email protected]>.\n"));
}