text: /*-------------------------------------------------------------------------
   *
   * 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).  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) 1996-2021, 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 "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;
  static uint32 set_xid_epoch = (uint32) -1;
  static TransactionId set_oldest_xid = 0;
  static TransactionId set_xid = 0;
  static TransactionId set_oldest_commit_ts_xid = 0;
  static TransactionId set_newest_commit_ts_xid = 0;
  static Oid	set_oid = 0;
  static MultiXactId set_mxid = 0;
  static MultiXactOffset set_mxoff = (MultiXactOffset) -1;
  static uint32 minXlogTli = 0;
  static XLogSegNo minXlogSegNo = 0;
  static int	WalSegSz;
  static int	set_wal_segsize;
  
  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 WriteEmptyXLOG(void);
  static void usage(void);
  
  
  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},
  		{NULL, 0, NULL, 0}
  	};
  
  	int			c;
  	bool		force = false;
  	bool		noupdate = false;
  	MultiXactId set_oldestmxid = 0;
  	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':
  				set_xid_epoch = strtoul(optarg, &endptr, 0);
  				if (endptr == optarg || *endptr != '\0')
  				{
  					/*------
  					  translator: the second %s is a command line argument (-e, etc) */
  					pg_log_error("invalid argument for option %s", "-e");
  					fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
  					exit(1);
  				}
  				if (set_xid_epoch == -1)
  				{
  					pg_log_error("transaction ID epoch (-e) must not be -1");
  					exit(1);
  				}
  				break;
  
  			case 'u':
  				set_oldest_xid = strtoul(optarg, &endptr, 0);
  				if (endptr == optarg || *endptr != '\0')
  				{
  					pg_log_error("invalid argument for option %s", "-u");
  					fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
  					exit(1);
  				}
  				if (!TransactionIdIsNormal(set_oldest_xid))
  				{
  					pg_log_error("oldest transaction ID (-u) must be greater or equal to %u", FirstNormalTransactionId);
  					exit(1);
  				}
  				break;
  
  			case 'x':
  				set_xid = strtoul(optarg, &endptr, 0);
  				if (endptr == optarg || *endptr != '\0')
  				{
  					pg_log_error("invalid argument for option %s", "-x");
  					fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
  					exit(1);
  				}
  				if (!TransactionIdIsNormal(set_xid))
  				{
  					pg_log_error("transaction ID (-x) must be greater or equal to %u", FirstNormalTransactionId);
  					exit(1);
  				}
  				break;
  
  			case 'c':
  				set_oldest_commit_ts_xid = strtoul(optarg, &endptr, 0);
  				if (endptr == optarg || *endptr != ',')
  				{
  					pg_log_error("invalid argument for option %s", "-c");
  					fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
  					exit(1);
  				}
  				set_newest_commit_ts_xid = strtoul(endptr + 1, &endptr2, 0);
  				if (endptr2 == endptr + 1 || *endptr2 != '\0')
  				{
  					pg_log_error("invalid argument for option %s", "-c");
  					fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
  					exit(1);
  				}
  
  				if (set_oldest_commit_ts_xid < 2 &&
  					set_oldest_commit_ts_xid != 0)
  				{
  					pg_log_error("transaction ID (-c) must be either 0 or greater than or equal to 2");
  					exit(1);
  				}
  
  				if (set_newest_commit_ts_xid < 2 &&
  					set_newest_commit_ts_xid != 0)
  				{
  					pg_log_error("transaction ID (-c) must be either 0 or greater than or equal to 2");
  					exit(1);
  				}
  				break;
  
  			case 'o':
  				set_oid = strtoul(optarg, &endptr, 0);
  				if (endptr == optarg || *endptr != '\0')
  				{
  					pg_log_error("invalid argument for option %s", "-o");
  					fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
  					exit(1);
  				}
  				if (set_oid == 0)
  				{
  					pg_log_error("OID (-o) must not be 0");
  					exit(1);
  				}
  				break;
  
  			case 'm':
  				set_mxid = strtoul(optarg, &endptr, 0);
  				if (endptr == optarg || *endptr != ',')
  				{
  					pg_log_error("invalid argument for option %s", "-m");
  					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')
  				{
  					pg_log_error("invalid argument for option %s", "-m");
  					fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
  					exit(1);
  				}
  				if (set_mxid == 0)
  				{
  					pg_log_error("multitransaction ID (-m) must not be 0");
  					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)
  				{
  					pg_log_error("oldest multitransaction ID (-m) must not be 0");
  					exit(1);
  				}
  				break;
  
  			case 'O':
  				set_mxoff = strtoul(optarg, &endptr, 0);
  				if (endptr == optarg || *endptr != '\0')
  				{
  					pg_log_error("invalid argument for option %s", "-O");
  					fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
  					exit(1);
  				}
  				if (set_mxoff == -1)
  				{
  					pg_log_error("multitransaction offset (-O) must not be -1");
  					exit(1);
  				}
  				break;
  
  			case 'l':
  				if (strspn(optarg, "01234567890ABCDEFabcdef") != XLOG_FNAME_LEN)
  				{
  					pg_log_error("invalid argument for option %s", "-l");
  					fprintf(stderr, _("Try \"%s --help\" for more information.\n"), 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:
  				set_wal_segsize = strtol(optarg, &endptr, 10) * 1024 * 1024;
  				if (endptr == optarg || *endptr != '\0')
  				{
  					pg_log_error("argument of --wal-segsize must be a number");
  					exit(1);
  				}
  				if (!IsValidWalSegSize(set_wal_segsize))
  				{
  					pg_log_error("argument of --wal-segsize must be a power of 2 between 1 and 1024");
  					exit(1);
  				}
  				break;
  
  			default:
  				fprintf(stderr, _("Try \"%s --help\" for more information.\n"), 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]);
  		fprintf(stderr, _("Try \"%s --help\" for more information.\n"),
  				progname);
  		exit(1);
  	}
  
  	if (DataDir == NULL)
  	{
  		pg_log_error("no data directory specified");
  		fprintf(stderr, _("Try \"%s --help\" for more information.\n"), 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_info("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_log_error("could not read permissions of directory \"%s\": %m",
  					 DataDir);
  		exit(1);
  	}
  
  	umask(pg_mode_mask);
  
  	if (chdir(DataDir) < 0)
  	{
  		pg_log_error("could not change directory to \"%s\": %m",
  					 DataDir);
  		exit(1);
  	}
  
  	/* 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_log_error("could not open file \"%s\" for reading: %m",
  						 "postmaster.pid");
  			exit(1);
  		}
  	}
  	else
  	{
  		pg_log_error("lock file \"%s\" exists", "postmaster.pid");
  		pg_log_info("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 (set_wal_segsize != 0)
  		WalSegSz = set_wal_segsize;
  	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 (set_xid_epoch != -1)
  		ControlFile.checkPointCopy.nextXid =
  			FullTransactionIdFromEpochAndXid(set_xid_epoch,
  											 XidFromFullTransactionId(ControlFile.checkPointCopy.nextXid));
  
  	if (set_oldest_xid != 0)
  	{
  		ControlFile.checkPointCopy.oldestXid = set_oldest_xid;
  		ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
  	}
  
  	if (set_xid != 0)
  		ControlFile.checkPointCopy.nextXid =
  			FullTransactionIdFromEpochAndXid(EpochFromFullTransactionId(ControlFile.checkPointCopy.nextXid),
  											 set_xid);
  
  	if (set_oldest_commit_ts_xid != 0)
  		ControlFile.checkPointCopy.oldestCommitTsXid = set_oldest_commit_ts_xid;
  	if (set_newest_commit_ts_xid != 0)
  		ControlFile.checkPointCopy.newestCommitTsXid = set_newest_commit_ts_xid;
  
  	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 (set_wal_segsize != 0)
  		ControlFile.xlog_seg_size = WalSegSz;
  
  	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)
  	{
  		PrintNewControlValues();
  		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 write-ahead 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(_("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)
  {
  	const char *ver_file = "PG_VERSION";
  	FILE	   *ver_fd;
  	char		rawline[64];
  
  	if ((ver_fd = fopen(ver_file, "r")) == NULL)
  	{
  		pg_log_error("could not open file \"%s\" for reading: %m",
  					 ver_file);
  		exit(1);
  	}
  
  	/* version number has to be the first line read */
  	if (!fgets(rawline, sizeof(rawline), ver_fd))
  	{
  		if (!ferror(ver_fd))
  			pg_log_error("unexpected empty file \"%s\"", ver_file);
  		else
  			pg_log_error("could not read file \"%s\": %m", ver_file);
  		exit(1);
  	}
  
  	/* strip trailing newline and carriage return */
  	(void) pg_strip_crlf(rawline);
  
  	if (strcmp(rawline, PG_MAJORVERSION) != 0)
  	{
  		pg_log_error("data directory is of wrong version");
  		pg_log_info("File \"%s\" contains \"%s\", which is not compatible with this program's version \"%s\".",
  					ver_file, rawline, PG_MAJORVERSION);
  		exit(1);
  	}
  
  	fclose(ver_fd);
  }
  
  
  /*
   * 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;
  	int			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_info("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_log_error("could not read file \"%s\": %m", XLOG_CONTROL_FILE);
  		exit(1);
  	}
  	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 = 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 = 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 = 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 = 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 = 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)
  {
  	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:           %llu\n"),
  		   (unsigned long long) 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:  %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(_("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(_("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);
  }
  
  
  /*
   * 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 (set_mxid != 0)
  	{
  		printf(_("NextMultiXactId:                      %u\n"),
  			   ControlFile.checkPointCopy.nextMulti);
  		printf(_("OldestMultiXid:                       %u\n"),
  			   ControlFile.checkPointCopy.oldestMulti);
  		printf(_("OldestMulti's DB:                     %u\n"),
  			   ControlFile.checkPointCopy.oldestMultiDB);
  	}
  
  	if (set_mxoff != -1)
  	{
  		printf(_("NextMultiOffset:                      %u\n"),
  			   ControlFile.checkPointCopy.nextMultiOffset);
  	}
  
  	if (set_oid != 0)
  	{
  		printf(_("NextOID:                              %u\n"),
  			   ControlFile.checkPointCopy.nextOid);
  	}
  
  	if (set_xid != 0)
  	{
  		printf(_("NextXID:                              %u\n"),
  			   XidFromFullTransactionId(ControlFile.checkPointCopy.nextXid));
  		printf(_("OldestXID:                            %u\n"),
  			   ControlFile.checkPointCopy.oldestXid);
  		printf(_("OldestXID's DB:                       %u\n"),
  			   ControlFile.checkPointCopy.oldestXidDB);
  	}
  
  	if (set_xid_epoch != -1)
  	{
  		printf(_("NextXID epoch:                        %u\n"),
  			   EpochFromFullTransactionId(ControlFile.checkPointCopy.nextXid));
  	}
  
  	if (set_oldest_commit_ts_xid != 0)
  	{
  		printf(_("oldestCommitTsXid:                    %u\n"),
  			   ControlFile.checkPointCopy.oldestCommitTsXid);
  	}
  	if (set_newest_commit_ts_xid != 0)
  	{
  		printf(_("newestCommitTsXid:                    %u\n"),
  			   ControlFile.checkPointCopy.newestCommitTsXid);
  	}
  
  	if (set_wal_segsize != 0)
  	{
  		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.time = (pg_time_t) time(NULL);
  	ControlFile.checkPoint = ControlFile.checkPointCopy.redo;
  	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.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 = 64;
  
  	/* 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		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_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_log_error("could not open directory \"%s\": %m", XLOGDIR);
  		exit(1);
  	}
  
  	while (errno = 0, (xlde = readdir(xldir)) != NULL)
  	{
  		if (IsXLogFileName(xlde->d_name) ||
  			IsPartialXLogFileName(xlde->d_name))
  		{
  			unsigned int tli,
  						log,
  						seg;
  			XLogSegNo	segno;
  
  			/*
  			 * Note: We don't use XLogFromFileName here, because we want to
  			 * use the segment size from the control file, not the size the
  			 * pg_resetwal binary was compiled with
  			 */
  			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;
  		}
  	}
  
  	if (errno)
  	{
  		pg_log_error("could not read directory \"%s\": %m", XLOGDIR);
  		exit(1);
  	}
  
  	if (closedir(xldir))
  	{
  		pg_log_error("could not close directory \"%s\": %m", XLOGDIR);
  		exit(1);
  	}
  
  	/*
  	 * 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_log_error("could not open directory \"%s\": %m", XLOGDIR);
  		exit(1);
  	}
  
  	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_log_error("could not delete file \"%s\": %m", path);
  				exit(1);
  			}
  		}
  	}
  
  	if (errno)
  	{
  		pg_log_error("could not read directory \"%s\": %m", XLOGDIR);
  		exit(1);
  	}
  
  	if (closedir(xldir))
  	{
  		pg_log_error("could not close directory \"%s\": %m", XLOGDIR);
  		exit(1);
  	}
  }
  
  
  /*
   * 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_log_error("could not open directory \"%s\": %m", ARCHSTATDIR);
  		exit(1);
  	}
  
  	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_log_error("could not delete file \"%s\": %m", path);
  				exit(1);
  			}
  		}
  	}
  
  	if (errno)
  	{
  		pg_log_error("could not read directory \"%s\": %m", ARCHSTATDIR);
  		exit(1);
  	}
  
  	if (closedir(xldir))
  	{
  		pg_log_error("could not close directory \"%s\": %m", ARCHSTATDIR);
  		exit(1);
  	}
  }
  
  
  /*
   * 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 = 0;
  	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_log_error("could not open file \"%s\": %m", path);
  		exit(1);
  	}
  
  	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_log_error("could not write file \"%s\": %m", path);
  		exit(1);
  	}
  
  	/* 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_log_error("could not write file \"%s\": %m", path);
  			exit(1);
  		}
  	}
  
  	if (fsync(fd) != 0)
  	{
  		pg_log_error("fsync error: %m");
  		exit(1);
  	}
  
  	close(fd);
  }
  
  
  static void
  usage(void)
  {
  	printf(_("%s resets the PostgreSQL write-ahead log.\n\n"), progname);
  	printf(_("Usage:\n  %s [OPTION]... DATADIR\n\n"), progname);
  	printf(_("Options:\n"));
  	printf(_("  -c, --commit-timestamp-ids=XID,XID\n"
  			 "                                   set oldest and newest transactions bearing\n"
  			 "                                   commit timestamp (zero means no change)\n"));
  	printf(_(" [-D, --pgdata=]DATADIR            data directory\n"));
  	printf(_("  -e, --epoch=XIDEPOCH             set next transaction ID epoch\n"));
  	printf(_("  -f, --force                      force update to be done\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(_("  -n, --dry-run                    no update, just show what would be done\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(_("  -V, --version                    output version information, then exit\n"));
  	printf(_("  -x, --next-transaction-id=XID    set next transaction ID\n"));
  	printf(_("      --wal-segsize=SIZE           size of WAL segments, in megabytes\n"));
  	printf(_("  -?, --help                       show this help, then exit\n"));
  	printf(_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
  	printf(_("%s home page: <%s>\n"), PACKAGE_NAME, PACKAGE_URL);
  }
  