pg_resetxlog.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * 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) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $PostgreSQL: pgsql/src/bin/pg_resetxlog/pg_resetxlog.c,v 1.38 2005/10/15 02:49:40 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#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/multixact.h"
#include "access/xlog.h"
#include "access/xlog_internal.h"
#include "catalog/catversion.h"
#include "catalog/pg_control.h"

extern int	optind;
extern char *optarg;


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

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


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

	set_pglocale_pgservice(argv[0], "pg_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:")) != -1)
	{
		switch (c)
		{
			case 'f':
				force = true;
				break;

			case 'n':
				noupdate = true;
				break;

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

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

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

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

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

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

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

	/*
	 * Don't allow pg_resetxlog to be run as root, to avoid overwriting the
	 * ownership of files in the data directory. We need only check for root
	 * -- any other user won't have sufficient permissions to modify files in
	 * the data directory.
	 */
#ifndef WIN32
#ifndef __BEOS__				/* no root check on BeOS */
	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
#endif

	DataDir = argv[optind];

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

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

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

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

	/*
	 * Adjust fields if required by switches.  (Do this now so that printout,
	 * if any, includes these values.)
	 */
	if (set_xid != 0)
		ControlFile.checkPointCopy.nextXid = set_xid;

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

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

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

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

	if (minXlogId > ControlFile.logId ||
		(minXlogId == ControlFile.logId &&
		 minXlogSeg > ControlFile.logSeg))
	{
		ControlFile.logId = minXlogId;
		ControlFile.logSeg = minXlogSeg;
	}

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

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

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

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


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

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

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

	len = read(fd, buffer, BLCKSZ);
	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"),