src/bin/pg_resetwal/pg_resetwal.c - master - githubmirror/postgres

src/bin/pg_resetwal/pg_resetwal.c
1 321 строка39 KB
Heikki Linnakangas
pg_resetwal: do not allow zero next multixact offset
27 июл 2026, 15:29
27 июл 2026, 15:292cad308
/*-------------------------------------------------------------------------
 *
 * pg_resetwal.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).
 *	  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) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/bin/pg_resetwal/pg_resetwal.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 <sys/stat.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>

#include "access/heaptoast.h"
#include "access/multixact.h"
#include "access/transam.h"
#include "access/xlog.h"
#include "access/xlog_internal.h"
#include "common/controldata_utils.h"
#include "common/fe_memutils.h"
#include "common/file_perm.h"
#include "common/logging.h"
#include "common/restricted_token.h"
#include "common/string.h"
#include "fe_utils/option_utils.h"
#include "fe_utils/version.h"
#include "getopt_long.h"
#include "pg_getopt.h"
#include "storage/large_object.h"

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;

/*
 * New values given on the command-line
 */
static bool next_xid_epoch_given = false;
static uint32 next_xid_epoch_val;

static bool oldest_xid_given = false;
static TransactionId oldest_xid_val;

static bool next_xid_given = false;
static TransactionId next_xid_val;

static bool commit_ts_xids_given = false;
static TransactionId oldest_commit_ts_xid_val;
static TransactionId newest_commit_ts_xid_val;

static bool next_oid_given = false;
static Oid	next_oid_val;

static bool mxids_given = false;
static MultiXactId next_mxid_val;
static MultiXactId oldest_mxid_val = 0;

static bool next_mxoff_given = false;
static MultiXactOffset next_mxoff_val;

static bool wal_segsize_given = false;
static int	wal_segsize_val;

static bool char_signedness_given = false;
static bool char_signedness_val;


static TimeLineID minXlogTli = 0;
static XLogSegNo minXlogSegNo = 0;
static int	WalSegSz;

static void CheckDataVersion(void);
static bool read_controlfile(void);
static void GuessControlValues(void);
static void PrintControlValues(bool guessed);
static void PrintNewControlValues(void);
static void RewriteControlFile(void);
static void FindEndOfXLOG(void);
static void KillExistingXLOG(void);
static void KillExistingArchiveStatus(void);
static void KillExistingWALSummaries(void);
static void WriteEmptyXLOG(void);
static void usage(void);
static uint32 strtouint32_strict(const char *restrict s, char **restrict endptr, int base);
static uint64 strtouint64_strict(const char *restrict s, char **restrict endptr, int base);


int
main(int argc, char *argv[])
{
	static struct option long_options[] = {
		{"commit-timestamp-ids", required_argument, NULL, 'c'},
		{"pgdata", required_argument, NULL, 'D'},
		{"epoch", required_argument, NULL, 'e'},
		{"force", no_argument, NULL, 'f'},
		{"next-wal-file", required_argument, NULL, 'l'},
		{"multixact-ids", required_argument, NULL, 'm'},
		{"dry-run", no_argument, NULL, 'n'},
		{"next-oid", required_argument, NULL, 'o'},
		{"multixact-offset", required_argument, NULL, 'O'},
		{"oldest-transaction-id", required_argument, NULL, 'u'},
		{"next-transaction-id", required_argument, NULL, 'x'},
		{"wal-segsize", required_argument, NULL, 1},
		{"char-signedness", required_argument, NULL, 2},
		{NULL, 0, NULL, 0}
	};

	int			c;
	bool		force = false;
	bool		noupdate = false;
	char	   *endptr;
	char	   *endptr2;
	char	   *DataDir = NULL;
	char	   *log_fname = NULL;
	int			fd;

	pg_logging_init(argv[0]);
	set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_resetwal"));
	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_resetwal (PostgreSQL) " PG_VERSION);
			exit(0);
		}
	}


	while ((c = getopt_long(argc, argv, "c:D:e:fl:m:no:O:u:x:", long_options, NULL)) != -1)
	{
		switch (c)
		{
			case 'D':
				DataDir = optarg;
				break;

			case 'f':
				force = true;
				break;

			case 'n':
				noupdate = true;
				break;

			case 'e':
				errno = 0;
				next_xid_epoch_val = strtouint32_strict(optarg, &endptr, 0);
				if (endptr == optarg || *endptr != '\0' || errno != 0)
				{
					/*------
					  translator: %s is a command line argument (-e, etc) */
					pg_log_error("invalid argument for option %s", "-e");
					pg_log_error_hint("Try \"%s --help\" for more information.", progname);
					exit(1);
				}
				next_xid_epoch_given = true;
				break;

			case 'u':
				errno = 0;
				oldest_xid_val = strtouint32_strict(optarg, &endptr, 0);
				if (endptr == optarg || *endptr != '\0' || errno != 0)
				{
					pg_log_error("invalid argument for option %s", "-u");
					pg_log_error_hint("Try \"%s --help\" for more information.", progname);
					exit(1);
				}
				if (!TransactionIdIsNormal(oldest_xid_val))
					pg_fatal("oldest transaction ID (-u) must be greater than or equal to %u", FirstNormalTransactionId);
				oldest_xid_given = true;
				break;

			case 'x':
				errno = 0;
				next_xid_val = strtouint32_strict(optarg, &endptr, 0);
				if (endptr == optarg || *endptr != '\0' || errno != 0)
				{
					pg_log_error("invalid argument for option %s", "-x");
					pg_log_error_hint("Try \"%s --help\" for more information.", progname);
					exit(1);
				}
				if (!TransactionIdIsNormal(next_xid_val))
					pg_fatal("transaction ID (-x) must be greater than or equal to %u", FirstNormalTransactionId);
				next_xid_given = true;
				break;

			case 'c':
				errno = 0;
				oldest_commit_ts_xid_val = strtouint32_strict(optarg, &endptr, 0);
				if (endptr == optarg || *endptr != ',' || errno != 0)
				{
					pg_log_error("invalid argument for option %s", "-c");
					pg_log_error_hint("Try \"%s --help\" for more information.", progname);
					exit(1);
				}
				newest_commit_ts_xid_val = strtoul(endptr + 1, &endptr2, 0);
				if (endptr2 == endptr + 1 || *endptr2 != '\0' || errno != 0)
				{
					pg_log_error("invalid argument for option %s", "-c");
					pg_log_error_hint("Try \"%s --help\" for more information.", progname);
					exit(1);
				}

				if (oldest_commit_ts_xid_val < FirstNormalTransactionId &&
					oldest_commit_ts_xid_val != InvalidTransactionId)
					pg_fatal("transaction ID (-c) must be either %u or greater than or equal to %u", InvalidTransactionId, FirstNormalTransactionId);

				if (newest_commit_ts_xid_val < FirstNormalTransactionId &&
					newest_commit_ts_xid_val != InvalidTransactionId)
					pg_fatal("transaction ID (-c) must be either %u or greater than or equal to %u", InvalidTransactionId, FirstNormalTransactionId);
				commit_ts_xids_given = true;
				break;

			case 'o':
				errno = 0;
				next_oid_val = strtouint32_strict(optarg, &endptr, 0);
				if (endptr == optarg || *endptr != '\0' || errno != 0)
				{
					pg_log_error("invalid argument for option %s", "-o");
					pg_log_error_hint("Try \"%s --help\" for more information.", progname);
					exit(1);
				}
				if (next_oid_val == 0)
					pg_fatal("OID (-o) must not be 0");
				next_oid_given = true;
				break;

			case 'm':
				errno = 0;
				next_mxid_val = strtouint32_strict(optarg, &endptr, 0);
				if (endptr == optarg || *endptr != ',' || errno != 0)
				{
					pg_log_error("invalid argument for option %s", "-m");
					pg_log_error_hint("Try \"%s --help\" for more information.", progname);
					exit(1);
				}

				oldest_mxid_val = strtouint32_strict(endptr + 1, &endptr2, 0);
				if (endptr2 == endptr + 1 || *endptr2 != '\0' || errno != 0)
				{
					pg_log_error("invalid argument for option %s", "-m");
					pg_log_error_hint("Try \"%s --help\" for more information.", 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 (next_mxid_val == 0)
					pg_fatal("next multitransaction ID (-m) must not be 0");
				if (oldest_mxid_val == 0)
					pg_fatal("oldest multitransaction ID (-m) must not be 0");
				mxids_given = true;
				break;

			case 'O':
				errno = 0;
				next_mxoff_val = strtouint64_strict(optarg, &endptr, 0);
				if (endptr == optarg || *endptr != '\0' || errno != 0)
				{
					pg_log_error("invalid argument for option %s", "-O");
					pg_log_error_hint("Try \"%s --help\" for more information.", progname);
					exit(1);
				}

				/* offset 0 means "invalid" in pg_multixact/offsets */
				if (next_mxoff_val == 0)
					pg_fatal("next multitransaction offset (-O) must not be 0");
				next_mxoff_given = true;
				break;

			case 'l':
				if (strspn(optarg, "0123456789ABCDEFabcdef") != XLOG_FNAME_LEN)
				{
					pg_log_error("invalid argument for option %s", "-l");
					pg_log_error_hint("Try \"%s --help\" for more information.", progname);
					exit(1);
				}

				/*
				 * XLogFromFileName requires wal segment size which is not yet
				 * set. Hence wal details are set later on.
				 */
				log_fname = pg_strdup(optarg);
				break;

			case 1:
				{
					int			wal_segsize_mb;

					if (!option_parse_int(optarg, "--wal-segsize", 1, 1024, &wal_segsize_mb))
						exit(1);
					wal_segsize_val = wal_segsize_mb * 1024 * 1024;
					if (!IsValidWalSegSize(wal_segsize_val))
						pg_fatal("argument of %s must be a power of two between 1 and 1024", "--wal-segsize");
					wal_segsize_given = true;
					break;
				}

			case 2:
				{
					errno = 0;

					if (pg_strcasecmp(optarg, "signed") == 0)
						char_signedness_val = true;
					else if (pg_strcasecmp(optarg, "unsigned") == 0)
						char_signedness_val = false;
					else
					{
						pg_log_error("invalid argument for option %s", "--char-signedness");
						pg_log_error_hint("Try \"%s --help\" for more information.", progname);
						exit(1);
					}
					char_signedness_given = true;
					break;
				}

			default:
				/* getopt_long already emitted a complaint */
				pg_log_error_hint("Try \"%s --help\" for more information.", progname);
				exit(1);
		}
	}

	if (DataDir == NULL && optind < argc)
		DataDir = argv[optind++];

	/* Complain if any arguments remain */
	if (optind < argc)
	{
		pg_log_error("too many command-line arguments (first is \"%s\")",
					 argv[optind]);
		pg_log_error_hint("Try \"%s --help\" for more information.", progname);
		exit(1);
	}

	if (DataDir == NULL)
	{
		pg_log_error("no data directory specified");
		pg_log_error_hint("Try \"%s --help\" for more information.", progname);
		exit(1);
	}

	/*
	 * Don't allow pg_resetwal 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)
	{
		pg_log_error("cannot be executed by \"root\"");
		pg_log_error_hint("You must run %s as the PostgreSQL superuser.",
						  progname);
		exit(1);
	}
#endif

	get_restricted_token();

	/* Set mask based on PGDATA permissions */
	if (!GetDataDirectoryCreatePerm(DataDir))
		pg_fatal("could not read permissions of directory \"%s\": %m",
				 DataDir);

	umask(pg_mode_mask);

	if (chdir(DataDir) < 0)
		pg_fatal("could not change directory to \"%s\": %m",
				 DataDir);

	/* Check that data directory matches our server version */
	CheckDataVersion();

	/*
	 * 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)
			pg_fatal("could not open file \"%s\" for reading: %m",
					 "postmaster.pid");
	}
	else
	{
		pg_log_error("lock file \"%s\" exists", "postmaster.pid");
		pg_log_error_hint("Is a server running?  If not, delete the lock file and try again.");
		exit(1);
	}

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

	/*
	 * If no new WAL segment size was specified, use the control file value.
	 */
	if (wal_segsize_given)
		WalSegSz = wal_segsize_val;
	else
		WalSegSz = ControlFile.xlog_seg_size;

	if (log_fname != NULL)
		XLogFromFileName(log_fname, &minXlogTli, &minXlogSegNo, WalSegSz);

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

	/*
	 * If we're not going to proceed with the reset, print the current control
	 * file parameters.
	 */
	if ((guessed && !force) || noupdate)
		PrintControlValues(guessed);

	/*
	 * Adjust fields if required by switches.  (Do this now so that printout,
	 * if any, includes these values.)
	 */
	if (next_xid_epoch_given)
		ControlFile.checkPointCopy.nextXid =
			FullTransactionIdFromEpochAndXid(next_xid_epoch_val,
											 XidFromFullTransactionId(ControlFile.checkPointCopy.nextXid));

	if (oldest_xid_given)
	{
		ControlFile.checkPointCopy.oldestXid = oldest_xid_val;
		ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
	}

	if (next_xid_given)
		ControlFile.checkPointCopy.nextXid =
			FullTransactionIdFromEpochAndXid(EpochFromFullTransactionId(ControlFile.checkPointCopy.nextXid),
											 next_xid_val);

	if (commit_ts_xids_given)
	{
		ControlFile.checkPointCopy.oldestCommitTsXid = oldest_commit_ts_xid_val;
		ControlFile.checkPointCopy.newestCommitTsXid = newest_commit_ts_xid_val;
	}

	if (next_oid_given)
		ControlFile.checkPointCopy.nextOid = next_oid_val;

	if (mxids_given)
	{
		ControlFile.checkPointCopy.nextMulti = next_mxid_val;

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

	if (next_mxoff_given)
		ControlFile.checkPointCopy.nextMultiOffset = next_mxoff_val;

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

	if (wal_segsize_given)
		ControlFile.xlog_seg_size = WalSegSz;

	if (char_signedness_given)
		ControlFile.default_char_signedness = char_signedness_val;

	if (minXlogSegNo > newXlogSegNo)
		newXlogSegNo = minXlogSegNo;

	if (noupdate)
	{
		PrintNewControlValues();
		exit(0);
	}

	/*
	 * If we had to guess anything, and -f was not given, just print the
	 * guessed values and exit.
	 */
	if (guessed && !force)
	{
		PrintNewControlValues();
		pg_log_error("not proceeding because control file values were guessed");
		pg_log_error_hint("If these values seem acceptable, use -f to force reset.");
		exit(1);
	}

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

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

	printf(_("Write-ahead log reset\n"));
	return 0;
}


/*
 * Look at the version string stored in PG_VERSION and decide if this utility
 * can be run safely or not.
 *
 * We don't want to inject pg_control and WAL files that are for a different
 * major version; that can't do anything good.  Note that we don't treat
 * mismatching version info in pg_control as a reason to bail out, because
 * recovering from a corrupted pg_control is one of the main reasons for this
 * program to exist at all.  However, PG_VERSION is unlikely to get corrupted,
 * and if it were it would be easy to fix by hand.  So let's make this check
 * to prevent simple user errors.
 */
static void
CheckDataVersion(void)
{
	char	   *version_str;
	uint32		version = get_pg_version(".", &version_str);

	if (GET_PG_MAJORVERSION_NUM(version) != PG_MAJORVERSION_NUM)
	{
		pg_log_error("data directory is of wrong version");
		pg_log_error_detail("File \"%s\" contains \"%s\", which is not compatible with this program's version \"%s\".",
							"PG_VERSION",
							version_str,
							PG_MAJORVERSION);
		exit(1);
	}
}


/*
 * 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
read_controlfile(void)
{
	int			fd;
	ssize_t		len;
	char	   *buffer;
	pg_crc32c	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.
		 */
		pg_log_error("could not open file \"%s\" for reading: %m",
					 XLOG_CONTROL_FILE);
		if (errno == ENOENT)
			pg_log_error_hint("If you are sure the data directory path is correct, execute\n"
							  "  touch %s\n"
							  "and try again.",
							  XLOG_CONTROL_FILE);
		exit(1);
	}

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

	len = read(fd, buffer, PG_CONTROL_FILE_SIZE);
	if (len < 0)
		pg_fatal("could not read file \"%s\": %m", XLOG_CONTROL_FILE);
	close(fd);

	if (len >= sizeof(ControlFileData) &&
		((ControlFileData *) buffer)->pg_control_version == PG_CONTROL_VERSION)
	{
		/* Check the CRC. */
		INIT_CRC32C(crc);
		COMP_CRC32C(crc,
					buffer,
					offsetof(ControlFileData, crc));
		FIN_CRC32C(crc);

		if (!EQ_CRC32C(crc, ((ControlFileData *) buffer)->crc))
		{
			/* We will use the data but treat it as guessed. */
			pg_log_warning("pg_control exists but has invalid CRC; proceed with caution");
			guessed = true;
		}

		memcpy(&ControlFile, buffer, sizeof(ControlFile));

		/* return false if WAL segment size is not valid */
		if (!IsValidWalSegSize(ControlFile.xlog_seg_size))
		{
			pg_log_warning(ngettext("pg_control specifies invalid WAL segment size (%d byte); proceed with caution",
									"pg_control specifies invalid WAL segment size (%d bytes); proceed with caution",
									ControlFile.xlog_seg_size),
						   ControlFile.xlog_seg_size);
			return false;
		}

		return true;
	}

	/* Looks like it's a mess. */
	pg_log_warning("pg_control exists but is broken or wrong version; ignoring it");
	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 |= ((uint64) tv.tv_usec) << 12;
	sysidentifier |= getpid() & 0xFFF;

	ControlFile.system_identifier = sysidentifier;

	ControlFile.checkPointCopy.redo = SizeOfXLogLongPHD;
	ControlFile.checkPointCopy.ThisTimeLineID = 1;
	ControlFile.checkPointCopy.PrevTimeLineID = 1;
	ControlFile.checkPointCopy.fullPageWrites = false;
	ControlFile.checkPointCopy.nextXid =
		FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId);
	ControlFile.checkPointCopy.nextOid = FirstGenbkiObjectId;
	ControlFile.checkPointCopy.nextMulti = FirstMultiXactId;
	ControlFile.checkPointCopy.nextMultiOffset = 1;
	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 = FirstNormalUnloggedLSN;

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

	ControlFile.wal_level = WAL_LEVEL_MINIMAL;
	ControlFile.wal_log_hints = false;
	ControlFile.track_commit_timestamp = false;
	ControlFile.MaxConnections = 100;
	ControlFile.max_wal_senders = 10;
	ControlFile.max_worker_processes = 8;
	ControlFile.max_prepared_xacts = 0;
	ControlFile.max_locks_per_xact = 128;

	ControlFile.maxAlign = MAXIMUM_ALIGNOF;
	ControlFile.floatFormat = FLOATFORMAT_VALUE;
	ControlFile.blcksz = BLCKSZ;
	ControlFile.relseg_size = RELSEG_SIZE;
	ControlFile.slru_pages_per_segment = SLRU_PAGES_PER_SEGMENT;
	ControlFile.xlog_blcksz = XLOG_BLCKSZ;
	ControlFile.xlog_seg_size = DEFAULT_XLOG_SEG_SIZE;
	ControlFile.nameDataLen = NAMEDATALEN;
	ControlFile.indexMaxKeys = INDEX_MAX_KEYS;
	ControlFile.toast_max_chunk_size = TOAST_MAX_CHUNK_SIZE;
	ControlFile.loblksize = LOBLKSIZE;
	ControlFile.float8ByVal = true; /* vestigial */

	/*
	 * 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)
{
	if (guessed)
		printf(_("Guessed pg_control values:\n\n"));
	else
		printf(_("Current pg_control values:\n\n"));

	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:           %" PRIu64 "\n"),
		   ControlFile.system_identifier);
	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"),
		   EpochFromFullTransactionId(ControlFile.checkPointCopy.nextXid),
		   XidFromFullTransactionId(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:  %" PRIu64 "\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(_("Latest checkpoint's oldestCommitTsXid:%u\n"),
		   ControlFile.checkPointCopy.oldestCommitTsXid);
	printf(_("Latest checkpoint's newestCommitTsXid:%u\n"),
		   ControlFile.checkPointCopy.newestCommitTsXid);
	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(_("Pages per SLRU segment:               %u\n"),
		   ControlFile.slru_pages_per_segment);
	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(_("Size of a large-object chunk:         %u\n"),
		   ControlFile.loblksize);
	/* This is no longer configurable, but users may still expect to see it: */
	printf(_("Date/time type storage:               %s\n"),
		   _("64-bit integers"));
	printf(_("Float8 argument passing:              %s\n"),
		   (ControlFile.float8ByVal ? _("by value") : _("by reference")));
	printf(_("Data page checksum version:           %u\n"),
		   ControlFile.data_checksum_version);
	printf(_("Default char data signedness:         %s\n"),
		   (ControlFile.default_char_signedness ? _("signed") : _("unsigned")));
}


/*
 * Print the values to be changed.
 */
static void
PrintNewControlValues(void)
{
	char		fname[MAXFNAMELEN];

	/* This will be always printed in order to keep format same. */
	printf(_("\n\nValues to be changed:\n\n"));

	XLogFileName(fname, ControlFile.checkPointCopy.ThisTimeLineID,
				 newXlogSegNo, WalSegSz);
	printf(_("First log segment after reset:        %s\n"), fname);

	if (mxids_given)
	{
		printf(_("NextMultiXactId:                      %u\n"),
			   ControlFile.checkPointCopy.nextMulti);
		printf(_("OldestMultiXid:                       %u\n"),
			   ControlFile.checkPointCopy.oldestMulti);
		printf(_("OldestMulti's DB:                     %u\n"),
			   ControlFile.checkPointCopy.oldestMultiDB);
	}

	if (next_mxoff_given)
	{
		printf(_("NextMultiOffset:                      %" PRIu64 "\n"),
			   ControlFile.checkPointCopy.nextMultiOffset);
	}

	if (next_oid_given)
	{
		printf(_("NextOID:                              %u\n"),
			   ControlFile.checkPointCopy.nextOid);
	}

	if (next_xid_given)
	{
		printf(_("NextXID:                              %u\n"),
			   XidFromFullTransactionId(ControlFile.checkPointCopy.nextXid));
	}

	if (oldest_xid_given)
	{
		printf(_("OldestXID:                            %u\n"),
			   ControlFile.checkPointCopy.oldestXid);
		printf(_("OldestXID's DB:                       %u\n"),
			   ControlFile.checkPointCopy.oldestXidDB);
	}

	if (next_xid_epoch_given)
	{
		printf(_("NextXID epoch:                        %u\n"),
			   EpochFromFullTransactionId(ControlFile.checkPointCopy.nextXid));
	}

	if (commit_ts_xids_given)
	{
		printf(_("oldestCommitTsXid:                    %u\n"),
			   ControlFile.checkPointCopy.oldestCommitTsXid);
		printf(_("newestCommitTsXid:                    %u\n"),
			   ControlFile.checkPointCopy.newestCommitTsXid);
	}

	if (wal_segsize_given)
	{
		printf(_("Bytes per WAL segment:                %u\n"),
			   ControlFile.xlog_seg_size);
	}
}


/*
 * Write out the new pg_control file.
 */
static void
RewriteControlFile(void)
{
	/*
	 * Adjust fields as needed to force an empty XLOG starting at
	 * newXlogSegNo.
	 */
	XLogSegNoOffsetToRecPtr(newXlogSegNo, SizeOfXLogLongPHD, WalSegSz,
							ControlFile.checkPointCopy.redo);
	ControlFile.checkPointCopy.time = (pg_time_t) time(NULL);

	ControlFile.state = DB_SHUTDOWNED;
	ControlFile.checkPoint = ControlFile.checkPointCopy.redo;
	ControlFile.minRecoveryPoint = InvalidXLogRecPtr;
	ControlFile.minRecoveryPointTLI = 0;
	ControlFile.backupStartPoint = InvalidXLogRecPtr;
	ControlFile.backupEndPoint = InvalidXLogRecPtr;
	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.wal_log_hints = false;
	ControlFile.track_commit_timestamp = false;
	ControlFile.MaxConnections = 100;
	ControlFile.max_wal_senders = 10;
	ControlFile.max_worker_processes = 8;
	ControlFile.max_prepared_xacts = 0;
	ControlFile.max_locks_per_xact = 128;

	/* The control file gets flushed here. */
	update_controlfile(".", &ControlFile, true);
}


/*
 * 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, newXlogSegNo is set to suitable
 * value for the beginning of replacement WAL (in our seg size).
 */
static void
FindEndOfXLOG(void)
{
	DIR		   *xldir;
	struct dirent *xlde;
	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.
	 */
	XLByteToSeg(ControlFile.checkPointCopy.redo, newXlogSegNo,
				ControlFile.xlog_seg_size);

	/*
	 * Scan the pg_wal 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)
		pg_fatal("could not open directory \"%s\": %m", XLOGDIR);

	while (errno = 0, (xlde = readdir(xldir)) != NULL)
	{
		if (IsXLogFileName(xlde->d_name) ||
			IsPartialXLogFileName(xlde->d_name))
		{
			TimeLineID	tli;
			XLogSegNo	segno;

			/* Use the segment size from the control file */
			XLogFromFileName(xlde->d_name, &tli, &segno,
							 ControlFile.xlog_seg_size);

			/*
			 * 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;
		}
	}

	if (errno)
		pg_fatal("could not read directory \"%s\": %m", XLOGDIR);

	if (closedir(xldir))
		pg_fatal("could not close directory \"%s\": %m", XLOGDIR);

	/*
	 * 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 + ControlFile.xlog_seg_size - 1) / WalSegSz;
	newXlogSegNo++;
}


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

	xldir = opendir(XLOGDIR);
	if (xldir == NULL)
		pg_fatal("could not open directory \"%s\": %m", XLOGDIR);

	while (errno = 0, (xlde = readdir(xldir)) != NULL)
	{
		if (IsXLogFileName(xlde->d_name) ||
			IsPartialXLogFileName(xlde->d_name))
		{
			snprintf(path, sizeof(path), "%s/%s", XLOGDIR, xlde->d_name);
			if (unlink(path) < 0)
				pg_fatal("could not delete file \"%s\": %m", path);
		}
	}

	if (errno)
		pg_fatal("could not read directory \"%s\": %m", XLOGDIR);

	if (closedir(xldir))
		pg_fatal("could not close directory \"%s\": %m", XLOGDIR);
}


/*
 * Remove existing archive status files
 */
static void
KillExistingArchiveStatus(void)
{
#define ARCHSTATDIR XLOGDIR "/archive_status"

	DIR		   *xldir;
	struct dirent *xlde;
	char		path[MAXPGPATH + sizeof(ARCHSTATDIR)];

	xldir = opendir(ARCHSTATDIR);
	if (xldir == NULL)
		pg_fatal("could not open directory \"%s\": %m", ARCHSTATDIR);

	while (errno = 0, (xlde = readdir(xldir)) != NULL)
	{
		if (strspn(xlde->d_name, "0123456789ABCDEF") == XLOG_FNAME_LEN &&
			(strcmp(xlde->d_name + XLOG_FNAME_LEN, ".ready") == 0 ||
			 strcmp(xlde->d_name + XLOG_FNAME_LEN, ".done") == 0 ||
			 strcmp(xlde->d_name + XLOG_FNAME_LEN, ".partial.ready") == 0 ||
			 strcmp(xlde->d_name + XLOG_FNAME_LEN, ".partial.done") == 0))
		{
			snprintf(path, sizeof(path), "%s/%s", ARCHSTATDIR, xlde->d_name);
			if (unlink(path) < 0)
				pg_fatal("could not delete file \"%s\": %m", path);
		}
	}

	if (errno)
		pg_fatal("could not read directory \"%s\": %m", ARCHSTATDIR);

	if (closedir(xldir))
		pg_fatal("could not close directory \"%s\": %m", ARCHSTATDIR);

#undef ARCHSTATDIR
}

/*
 * Remove existing WAL summary files
 */
static void
KillExistingWALSummaries(void)
{
#define WALSUMMARYDIR XLOGDIR	"/summaries"
#define WALSUMMARY_NHEXCHARS	40

	DIR		   *xldir;
	struct dirent *xlde;
	char		path[MAXPGPATH + sizeof(WALSUMMARYDIR)];

	xldir = opendir(WALSUMMARYDIR);
	if (xldir == NULL)
		pg_fatal("could not open directory \"%s\": %m", WALSUMMARYDIR);

	while (errno = 0, (xlde = readdir(xldir)) != NULL)
	{
		if (strspn(xlde->d_name, "0123456789ABCDEF") == WALSUMMARY_NHEXCHARS &&
			strcmp(xlde->d_name + WALSUMMARY_NHEXCHARS, ".summary") == 0)
		{
			snprintf(path, sizeof(path), "%s/%s", WALSUMMARYDIR, xlde->d_name);
			if (unlink(path) < 0)
				pg_fatal("could not delete file \"%s\": %m", path);
		}
	}

	if (errno)
		pg_fatal("could not read directory \"%s\": %m", WALSUMMARYDIR);

	if (closedir(xldir))
		pg_fatal("could not close directory \"%s\": %m", WALSUMMARYDIR);

#undef WALSUMMARY_NHEXCHARS
#undef WALSUMMARYDIR
}

/*
 * Write an empty XLOG file, containing only the checkpoint record
 * already set up in ControlFile.
 */
static void
WriteEmptyXLOG(void)
{
	PGAlignedXLogBlock buffer;
	XLogPageHeader page;
	XLogLongPageHeader longpage;
	XLogRecord *record;
	pg_crc32c	crc;
	char		path[MAXPGPATH];
	int			fd;
	int			nbytes;
	char	   *recptr;

	memset(buffer.data, 0, XLOG_BLCKSZ);

	/* Set up the XLOG page header */
	page = (XLogPageHeader) buffer.data;
	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 = WalSegSz;
	longpage->xlp_xlog_blcksz = XLOG_BLCKSZ;

	/* Insert the initial checkpoint record */
	recptr = (char *) page + SizeOfXLogLongPHD;
	record = (XLogRecord *) recptr;
	record->xl_prev = InvalidXLogRecPtr;
	record->xl_xid = InvalidTransactionId;
	record->xl_tot_len = SizeOfXLogRecord + SizeOfXLogRecordDataHeaderShort + sizeof(CheckPoint);
	record->xl_info = XLOG_CHECKPOINT_SHUTDOWN;
	record->xl_rmid = RM_XLOG_ID;

	recptr += SizeOfXLogRecord;
	*(recptr++) = (char) XLR_BLOCK_ID_DATA_SHORT;
	*(recptr++) = sizeof(CheckPoint);
	memcpy(recptr, &ControlFile.checkPointCopy,
		   sizeof(CheckPoint));

	INIT_CRC32C(crc);
	COMP_CRC32C(crc, ((char *) record) + SizeOfXLogRecord, record->xl_tot_len - SizeOfXLogRecord);
	COMP_CRC32C(crc, (char *) record, offsetof(XLogRecord, xl_crc));
	FIN_CRC32C(crc);
	record->xl_crc = crc;

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

	unlink(path);

	fd = open(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
			  pg_file_create_mode);
	if (fd < 0)
		pg_fatal("could not open file \"%s\": %m", path);

	errno = 0;
	if (write(fd, buffer.data, XLOG_BLCKSZ) != XLOG_BLCKSZ)
	{
		/* if write didn't set errno, assume problem is no disk space */
		if (errno == 0)
			errno = ENOSPC;
		pg_fatal("could not write file \"%s\": %m", path);
	}

	/* Fill the rest of the file with zeroes */
	memset(buffer.data, 0, XLOG_BLCKSZ);
	for (nbytes = XLOG_BLCKSZ; nbytes < WalSegSz; nbytes += XLOG_BLCKSZ)
	{
		errno = 0;
		if (write(fd, buffer.data, XLOG_BLCKSZ) != XLOG_BLCKSZ)
		{
			if (errno == 0)
				errno = ENOSPC;
			pg_fatal("could not write file \"%s\": %m", path);
		}
	}

	if (fsync(fd) != 0)
		pg_fatal("fsync error: %m");

	close(fd);
}


static void
usage(void)
{
	printf(_("%s resets the PostgreSQL write-ahead log.\n\n"), progname);
	printf(_("Usage:\n"));
	printf(_("  %s [OPTION]... DATADIR\n"), progname);

	printf(_("\nOptions:\n"));
	printf(_(" [-D, --pgdata=]DATADIR  data directory\n"));
	printf(_("  -f, --force            force update to be done even after unclean shutdown or\n"
			 "                         if pg_control values had to be guessed\n"));
	printf(_("  -n, --dry-run          no update, just show what would be done\n"));
	printf(_("  -V, --version          output version information, then exit\n"));
	printf(_("  -?, --help             show this help, then exit\n"));

	printf(_("\nOptions to override control file values:\n"));
	printf(_("  -c, --commit-timestamp-ids=XID,XID\n"
			 "                                   set oldest and newest transactions bearing\n"
			 "                                   commit timestamp (zero means no change)\n"));
	printf(_("  -e, --epoch=XIDEPOCH             set next transaction ID epoch\n"));
	printf(_("  -l, --next-wal-file=WALFILE      set minimum starting location for new WAL\n"));
	printf(_("  -m, --multixact-ids=MXID,MXID    set next and oldest multitransaction ID\n"));
	printf(_("  -o, --next-oid=OID               set next OID\n"));
	printf(_("  -O, --multixact-offset=OFFSET    set next multitransaction offset\n"));
	printf(_("  -u, --oldest-transaction-id=XID  set oldest transaction ID\n"));
	printf(_("  -x, --next-transaction-id=XID    set next transaction ID\n"));
	printf(_("      --char-signedness=OPTION     set char signedness to \"signed\" or \"unsigned\"\n"));
	printf(_("      --wal-segsize=SIZE           size of WAL segments, in megabytes\n"));

	printf(_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
	printf(_("%s home page: <%s>\n"), PACKAGE_NAME, PACKAGE_URL);
}

/*
 * strtouint32_strict -- like strtoul(), but returns uint32 and doesn't accept
 * negative values
 */
static uint32
strtouint32_strict(const char *restrict s, char **restrict endptr, int base)
{
	unsigned long val;
	bool		is_neg;

	/* skip leading whitespace */
	while (isspace((unsigned char) *s))
		s++;

	/*
	 * Is it negative?  We still call strtoul() if it was, to set 'endptr'.
	 * (The current callers don't care though.)
	 */
	is_neg = (*s == '-');

	val = strtoul(s, endptr, base);

	/* reject if it was negative */
	if (errno == 0 && is_neg)
	{
		errno = ERANGE;
		val = 0;
	}

	/*
	 * reject values larger than UINT32_MAX on platforms where long is 64 bits
	 * wide.
	 */
	if (errno == 0 && val != (uint32) val)
	{
		errno = ERANGE;
		val = UINT32_MAX;
	}

	return (uint32) val;
}

/*
 * strtouint64_strict -- like strtou64(), but doesn't accept negative values
 */
static uint64
strtouint64_strict(const char *restrict s, char **restrict endptr, int base)
{
	uint64		val;
	bool		is_neg;

	/* skip leading whitespace */
	while (isspace((unsigned char) *s))
		s++;

	/*
	 * Is it negative?  We still call strtou64() if it was, to set 'endptr'.
	 * (The current callers don't care though.)
	 */
	is_neg = (*s == '-');

	val = strtou64(s, endptr, base);

	/* reject if it was negative */
	if (errno == 0 && is_neg)
	{
		errno = ERANGE;
		val = 0;
	}

	return val;
}