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[PATCH 4/5] Add pg_xlogdump contrib module

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Cc: Andres Freund <andres(at)anarazel(dot)de>
Subject: [PATCH 4/5] Add pg_xlogdump contrib module
Date: 2013-01-08 19:09:46
Message-ID: 1357672187-7693-5-git-send-email-andres@2ndquadrant.com (view raw or flat)
Thread:
Lists: pgsql-hackers
From: Andres Freund <andres(at)anarazel(dot)de>

Authors: Andres Freund, Heikki Linnakangas
---
 contrib/Makefile                  |   1 +
 contrib/pg_xlogdump/Makefile      |  37 +++
 contrib/pg_xlogdump/compat.c      |  58 ++++
 contrib/pg_xlogdump/pg_xlogdump.c | 654 ++++++++++++++++++++++++++++++++++++++
 contrib/pg_xlogdump/tables.c      |  78 +++++
 doc/src/sgml/ref/allfiles.sgml    |   1 +
 doc/src/sgml/ref/pg_xlogdump.sgml |  76 +++++
 doc/src/sgml/reference.sgml       |   1 +
 src/backend/access/transam/rmgr.c |   1 +
 src/backend/catalog/catalog.c     |   2 +
 src/tools/msvc/Mkvcbuild.pm       |  16 +-
 11 files changed, 924 insertions(+), 1 deletion(-)
 create mode 100644 contrib/pg_xlogdump/Makefile
 create mode 100644 contrib/pg_xlogdump/compat.c
 create mode 100644 contrib/pg_xlogdump/pg_xlogdump.c
 create mode 100644 contrib/pg_xlogdump/tables.c
 create mode 100644 doc/src/sgml/ref/pg_xlogdump.sgml

diff --git a/contrib/Makefile b/contrib/Makefile
index fcd7c1e..5d290b8 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -39,6 +39,7 @@ SUBDIRS = \
 		pg_trgm		\
 		pg_upgrade	\
 		pg_upgrade_support \
+		pg_xlogdump	\
 		pgbench		\
 		pgcrypto	\
 		pgrowlocks	\
diff --git a/contrib/pg_xlogdump/Makefile b/contrib/pg_xlogdump/Makefile
new file mode 100644
index 0000000..1adef35
--- /dev/null
+++ b/contrib/pg_xlogdump/Makefile
@@ -0,0 +1,37 @@
+# contrib/pg_xlogdump/Makefile
+
+PGFILEDESC = "pg_xlogdump"
+PGAPPICON=win32
+
+PROGRAM = pg_xlogdump
+OBJS =  pg_xlogdump.o compat.o tables.o xlogreader.o $(RMGRDESCOBJS) \
+	$(WIN32RES)
+
+# XXX: Perhaps this should be done by a wildcard rule so that you don't need
+# to remember to add new rmgrdesc files to this list.
+RMGRDESCSOURCES = clogdesc.c dbasedesc.c gindesc.c gistdesc.c hashdesc.c \
+	heapdesc.c mxactdesc.c nbtdesc.c relmapdesc.c seqdesc.c smgrdesc.c \
+	spgdesc.c standbydesc.c tblspcdesc.c xactdesc.c xlogdesc.c
+
+RMGRDESCOBJS = $(patsubst %.c,%.o,$(RMGRDESCSOURCES))
+
+EXTRA_CLEAN = $(RMGRDESCSOURCES) xlogreader.c
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/pg_xlogdump
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
+
+override CPPFLAGS := -DFRONTEND $(CPPFLAGS)
+
+xlogreader.c: % : $(top_srcdir)/src/backend/access/transam/%
+	rm -f $@ && $(LN_S) $< .
+
+$(RMGRDESCSOURCES): % : $(top_srcdir)/src/backend/access/rmgrdesc/%
+	rm -f $@ && $(LN_S) $< .
diff --git a/contrib/pg_xlogdump/compat.c b/contrib/pg_xlogdump/compat.c
new file mode 100644
index 0000000..e150afb
--- /dev/null
+++ b/contrib/pg_xlogdump/compat.c
@@ -0,0 +1,58 @@
+/*-------------------------------------------------------------------------
+ *
+ * compat.c
+ *		Reimplementations of various backend functions.
+ *
+ * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		contrib/pg_xlogdump/compat.c
+ *
+ * This file contains client-side implementations for various backend
+ * functions that the rm_desc functions in *desc.c files rely on.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/* ugly hack, same as in e.g pg_controldata */
+#define FRONTEND 1
+#include "postgres.h"
+
+#include "catalog/catalog.h"
+#include "datatype/timestamp.h"
+#include "lib/stringinfo.h"
+#include "storage/relfilenode.h"
+#include "utils/timestamp.h"
+#include "utils/datetime.h"
+
+const char *
+timestamptz_to_str(TimestampTz dt)
+{
+	return "unimplemented-timestamp";
+}
+
+const char *
+relpathbackend(RelFileNode rnode, BackendId backend, ForkNumber forknum)
+{
+	return "unimplemented-relpathbackend";
+}
+
+/*
+ * Provide a hacked up compat layer for StringInfos so xlog desc functions can
+ * be linked/called.
+ */
+void
+appendStringInfo(StringInfo str, const char *fmt, ...)
+{
+	va_list		args;
+
+	va_start(args, fmt);
+	vprintf(fmt, args);
+	va_end(args);
+}
+
+void
+appendStringInfoString(StringInfo str, const char *string)
+{
+	appendStringInfo(str, "%s", string);
+}
diff --git a/contrib/pg_xlogdump/pg_xlogdump.c b/contrib/pg_xlogdump/pg_xlogdump.c
new file mode 100644
index 0000000..29ee73e
--- /dev/null
+++ b/contrib/pg_xlogdump/pg_xlogdump.c
@@ -0,0 +1,654 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_xlogdump.c - decode and display WAL
+ *
+ * Copyright (c) 2012, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		  contrib/pg_xlogdump/pg_xlogdump.c
+ *-------------------------------------------------------------------------
+ */
+
+/* ugly hack, same as in e.g pg_controldata */
+#define FRONTEND 1
+#include "postgres.h"
+
+#include <unistd.h>
+
+#include "access/xlog.h"
+#include "access/xlogreader.h"
+#include "access/rmgr.h"
+#include "access/transam.h"
+
+#include "catalog/catalog.h"
+
+#include "getopt_long.h"
+
+static const char *progname;
+
+typedef struct XLogDumpPrivateData
+{
+	TimeLineID	timeline;
+	char	   *inpath;
+	XLogRecPtr	startptr;
+	XLogRecPtr	endptr;
+
+	/* display options */
+	bool		bkp_details;
+	int			stop_after_records;
+	int			already_displayed_records;
+
+	/* filter options */
+	int         filter_by_rmgr;
+	TransactionId filter_by_xid;
+} XLogDumpPrivateData;
+
+static void fatal_error(const char *fmt, ...)
+__attribute__((format(PG_PRINTF_ATTRIBUTE, 1, 2)));
+
+static void fatal_error(const char *fmt, ...)
+{
+	va_list		args;
+	fflush(stdout);
+
+	fprintf(stderr, "%s: fatal_error: ", progname);
+	va_start(args, fmt);
+	vfprintf(stderr, fmt, args);
+	va_end(args);
+	fputc('\n', stderr);
+	exit(EXIT_FAILURE);
+}
+
+/*
+ * Check whether directory exists and whether we can open it. Keep errno set
+ * error reporting by the caller.
+ */
+static bool
+verify_directory(const char *directory)
+{
+	int fd = open(directory, O_DIRECTORY|O_RDONLY);
+	if (fd < 0)
+		return false;
+	close(fd);
+	return true;
+}
+
+static void
+split_path(const char *path, char **dir, char **fname)
+{
+	char *sep;
+
+	/* split filepath into directory & filename */
+	sep = strrchr(path, '/');
+
+	/* directory path */
+	if (sep != NULL)
+	{
+		/* windows doesn't have strndup */
+		*dir = strdup(path);
+		(*dir)[(sep - path) + 1] = '\0';
+		*fname = strdup(sep + 1);
+		}
+	/* local directory */
+	else
+	{
+		*dir = NULL;
+		*fname = strdup(path);
+	}
+}
+
+/*
+ * Try to find the file in several places:
+ * if directory == NULL:
+ *   fname
+ *   XLOGDIR / fname
+ *   $PGDATA / XLOGDIR / fname
+ * else
+ *   directory / fname
+ *   directory / XLOGDIR / fname
+ *
+ * return a read only fd
+ */
+static int
+fuzzy_open_file(const char *directory, const char *fname)
+{
+	int fd = -1;
+	char fpath[MAXPGPATH];
+
+	if (directory == NULL)
+	{
+		const char* datadir;
+
+		/* fname */
+		fd = open(fname, O_RDONLY | PG_BINARY, 0);
+		if (fd < 0 && errno != ENOENT)
+			return -1;
+		else if (fd > 0)
+			return fd;
+
+		/* XLOGDIR / fname */
+		snprintf(fpath, MAXPGPATH, "%s/%s",
+				 XLOGDIR, fname);
+		fd = open(fpath, O_RDONLY | PG_BINARY, 0);
+		if (fd < 0 && errno != ENOENT)
+			return -1;
+		else if (fd > 0)
+			return fd;
+
+		datadir = getenv("PGDATA");
+		/* $PGDATA / XLOGDIR / fname */
+		if (datadir != NULL)
+		{
+			snprintf(fpath, MAXPGPATH, "%s/%s/%s",
+					 datadir, XLOGDIR, fname);
+			fd = open(fpath, O_RDONLY | PG_BINARY, 0);
+			if (fd < 0 && errno != ENOENT)
+				return -1;
+			else if (fd > 0)
+				return fd;
+		}
+	}
+	else
+	{
+		/* directory / fname */
+		snprintf(fpath, MAXPGPATH, "%s/%s",
+				 directory, fname);
+		fd = open(fpath, O_RDONLY | PG_BINARY, 0);
+		if (fd < 0 && errno != ENOENT)
+			return -1;
+		else if (fd > 0)
+			return fd;
+
+		/* directory / XLOGDIR / fname */
+		snprintf(fpath, MAXPGPATH, "%s/%s/%s",
+				 directory, XLOGDIR, fname);
+		fd = open(fpath, O_RDONLY | PG_BINARY, 0);
+		if (fd < 0 && errno != ENOENT)
+			return -1;
+		else if (fd > 0)
+			return fd;
+	}
+	return -1;
+}
+
+/* this should probably be put in a general implementation */
+static void
+XLogDumpXLogRead(const char *directory, TimeLineID timeline_id,
+				 XLogRecPtr startptr, char *buf, Size count)
+{
+	char	   *p;
+	XLogRecPtr	recptr;
+	Size		nbytes;
+
+	static int	sendFile = -1;
+	static XLogSegNo sendSegNo = 0;
+	static uint32 sendOff = 0;
+
+	p = buf;
+	recptr = startptr;
+	nbytes = count;
+
+	while (nbytes > 0)
+	{
+		uint32		startoff;
+		int			segbytes;
+		int			readbytes;
+
+		startoff = recptr % XLogSegSize;
+
+		if (sendFile < 0 || !XLByteInSeg(recptr, sendSegNo))
+		{
+			char		fname[MAXFNAMELEN];
+
+			/* Switch to another logfile segment */
+			if (sendFile >= 0)
+				close(sendFile);
+
+			XLByteToSeg(recptr, sendSegNo);
+
+			XLogFileName(fname, timeline_id, sendSegNo);
+
+			sendFile = fuzzy_open_file(directory, fname);
+
+			if (sendFile < 0)
+				fatal_error("could not find file \"%s\": %s",
+							fname, strerror(errno));
+			sendOff = 0;
+		}
+
+		/* Need to seek in the file? */
+		if (sendOff != startoff)
+		{
+			if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
+			{
+				int		err = errno;
+				char	fname[MAXPGPATH];
+				XLogFileName(fname, timeline_id, sendSegNo);
+
+				fatal_error("could not seek in log segment %s to offset %u: %s",
+							fname, startoff, strerror(err));
+			}
+			sendOff = startoff;
+		}
+
+		/* How many bytes are within this segment? */
+		if (nbytes > (XLogSegSize - startoff))
+			segbytes = XLogSegSize - startoff;
+		else
+			segbytes = nbytes;
+
+		readbytes = read(sendFile, p, segbytes);
+		if (readbytes <= 0)
+		{
+			int		err = errno;
+			char	fname[MAXPGPATH];
+			XLogFileName(fname, timeline_id, sendSegNo);
+
+			fatal_error("could not read from log segment %s, offset %d, length %d: %s",
+						fname, sendOff, segbytes, strerror(err));
+		}
+
+		/* Update state for read */
+		recptr += readbytes;
+
+		sendOff += readbytes;
+		nbytes -= readbytes;
+		p += readbytes;
+	}
+}
+
+static int
+XLogDumpReadPage(XLogReaderState *state, XLogRecPtr targetPagePtr, int reqLen,
+				 char *readBuff, TimeLineID *curFileTLI)
+{
+	XLogDumpPrivateData *private = state->private_data;
+	int			count = XLOG_BLCKSZ;
+
+	if (private->endptr != InvalidXLogRecPtr)
+	{
+		if (targetPagePtr + XLOG_BLCKSZ <= private->endptr)
+			count = XLOG_BLCKSZ;
+		else if (targetPagePtr + reqLen <= private->endptr)
+			count = private->endptr - targetPagePtr;
+		else
+			return -1;
+	}
+
+	XLogDumpXLogRead(private->inpath, private->timeline, targetPagePtr,
+					 readBuff, count);
+
+	return count;
+}
+
+static void
+XLogDumpDisplayRecord(XLogReaderState *state, XLogRecord *record)
+{
+	XLogDumpPrivateData *config = (XLogDumpPrivateData *) state->private_data;
+	const RmgrData *rmgr = &RmgrTable[record->xl_rmid];
+
+	if (config->filter_by_rmgr != -1 &&
+	    config->filter_by_rmgr != record->xl_rmid)
+		return;
+
+	if (TransactionIdIsValid(config->filter_by_xid) &&
+	    config->filter_by_xid != record->xl_xid)
+		return;
+
+	config->already_displayed_records++;
+
+	printf("xlog record: rmgr: %-11s, record_len: %6u, tot_len: %6u, tx: %10u, lsn: %X/%08X, prev %X/%08X, bkp: %u%u%u%u, desc:",
+			rmgr->rm_name,
+			record->xl_len, record->xl_tot_len,
+			record->xl_xid,
+			(uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr,
+			(uint32) (record->xl_prev >> 32), (uint32) record->xl_prev,
+			!!(XLR_BKP_BLOCK(0) & record->xl_info),
+			!!(XLR_BKP_BLOCK(1) & record->xl_info),
+			!!(XLR_BKP_BLOCK(2) & record->xl_info),
+			!!(XLR_BKP_BLOCK(3) & record->xl_info));
+
+	/* the desc routine will printf the description directly to stdout */
+	rmgr->rm_desc(NULL, record->xl_info, XLogRecGetData(record));
+
+	putchar('\n');
+
+	if (config->bkp_details)
+	{
+		int		off;
+		char   *blk = (char *) XLogRecGetData(record) + record->xl_len;
+
+		for (off = 0; off < XLR_MAX_BKP_BLOCKS; off++)
+		{
+			BkpBlock	bkpb;
+
+			if (!(XLR_BKP_BLOCK(off) & record->xl_info))
+				continue;
+
+			memcpy(&bkpb, blk, sizeof(BkpBlock));
+			blk += sizeof(BkpBlock);
+			blk += BLCKSZ - bkpb.hole_length;
+
+			printf("\tbackup bkp #%u; rel %u/%u/%u; fork: %s; block: %u; hole: offset: %u, length: %u\n",
+				   off, bkpb.node.spcNode, bkpb.node.dbNode, bkpb.node.relNode,
+				   forkNames[bkpb.fork], bkpb.block, bkpb.hole_offset, bkpb.hole_length);
+		}
+	}
+}
+
+static void
+usage(void)
+{
+	printf("%s: reads/writes postgres transaction logs for debugging.\n\n",
+		   progname);
+	printf("Usage:\n");
+	printf("  %s [OPTION] [STARTSEG [ENDSEG]] \n", progname);
+	printf("\nOptions:\n");
+	printf("  -b, --bkp-details      output detailed information about backup blocks\n");
+	printf("  -e, --end RECPTR       read wal up to RECPTR\n");
+	printf("  -h, --help             show this help, then exit\n");
+	printf("  -n, --limit RECORDS    only display n records, abort afterwards\n");
+	printf("  -p, --path PATH        from where do we want to read? cwd/pg_xlog is the default\n");
+	printf("  -r, --rmgr RMGR        only show records generated by the rmgr RMGR\n");
+	printf("  -s, --start RECPTR     read wal in directory indicated by -p starting at RECPTR\n");
+	printf("  -t, --timeline TLI     which timeline do we want to read, defaults to 1\n");
+	printf("  -V, --version          output version information, then exit\n");
+	printf("  -x, --xid XID          only show records with transactionid XID\n");
+}
+
+int
+main(int argc, char **argv)
+{
+	uint32		xlogid;
+	uint32		xrecoff;
+	XLogReaderState *xlogreader_state;
+	XLogDumpPrivateData private;
+	XLogRecord *record;
+	XLogRecPtr	first_record;
+	char	   *errormsg;
+
+	static struct option long_options[] = {
+		{"bkp-details", no_argument, NULL, 'b'},
+		{"end", required_argument, NULL, 'e'},
+		{"help", no_argument, NULL, '?'},
+		{"limit", required_argument, NULL, 'n'},
+		{"path", required_argument, NULL, 'p'},
+		{"rmgr", required_argument, NULL, 'r'},
+		{"start", required_argument, NULL, 's'},
+		{"timeline", required_argument, NULL, 't'},
+		{"xid", required_argument, NULL, 'x'},
+		{"version", no_argument, NULL, 'V'},
+		{NULL, 0, NULL, 0}
+	};
+
+	int			option;
+	int			optindex = 0;
+
+	progname = get_progname(argv[0]);
+
+	memset(&private, 0, sizeof(XLogDumpPrivateData));
+
+	private.timeline = 1;
+	private.bkp_details = false;
+	private.startptr = InvalidXLogRecPtr;
+	private.endptr = InvalidXLogRecPtr;
+	private.stop_after_records = -1;
+	private.already_displayed_records = 0;
+	private.filter_by_rmgr = -1;
+	private.filter_by_xid = InvalidTransactionId;
+
+	if (argc <= 1)
+	{
+		fprintf(stderr, "%s: no arguments specified\n", progname);
+		goto bad_argument;
+	}
+
+	while ((option = getopt_long(argc, argv, "be:?n:p:r:s:t:Vx:",
+								 long_options, &optindex)) != -1)
+	{
+		switch (option)
+		{
+			case 'b':
+				private.bkp_details = true;
+				break;
+			case 'e':
+				if (sscanf(optarg, "%X/%X", &xlogid, &xrecoff) != 2)
+				{
+					fprintf(stderr, "%s: could not parse parse --end %s\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				private.endptr = (uint64)xlogid << 32 | xrecoff;
+				break;
+			case '?':
+				usage();
+				exit(EXIT_SUCCESS);
+				break;
+			case 'n':
+				if (sscanf(optarg, "%d", &private.stop_after_records) != 1)
+				{
+					fprintf(stderr, "%s: could not parse parse --limit %s\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				break;
+			case 'p':
+				private.inpath = strdup(optarg);
+				break;
+			case 'r':
+			{
+				int i;
+				for (i = 0; i < RM_MAX_ID; i++)
+				{
+					if (strcmp(optarg, RmgrTable[i].rm_name) == 0)
+					{
+						private.filter_by_rmgr = i;
+						break;
+					}
+				}
+
+				if (private.filter_by_rmgr == -1)
+				{
+					fprintf(stderr, "%s: --rmgr %s does not exist\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+			}
+			break;
+			case 's':
+				if (sscanf(optarg, "%X/%X", &xlogid, &xrecoff) != 2)
+				{
+					fprintf(stderr, "%s: could not parse parse --end %s\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				else
+					private.startptr = (uint64)xlogid << 32 | xrecoff;
+				break;
+			case 't':
+				if (sscanf(optarg, "%d", &private.timeline) != 1)
+				{
+					fprintf(stderr, "%s: could not parse timeline --timeline %s\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				break;
+			case 'V':
+				puts("pg_xlogdump (PostgreSQL) " PG_VERSION);
+				exit(EXIT_SUCCESS);
+				break;
+			case 'x':
+				if (sscanf(optarg, "%u", &private.filter_by_xid) != 1)
+				{
+					fprintf(stderr, "%s: could not parse --xid %s as a valid xid\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				break;
+			default:
+				goto bad_argument;
+		}
+	}
+
+	if ((optind + 2) < argc)
+	{
+		fprintf(stderr,
+				"%s: too many command-line arguments (first is \"%s\")\n",
+				progname, argv[optind + 2]);
+		goto bad_argument;
+	}
+
+	if (private.inpath != NULL)
+	{
+		/* validdate path points to directory */
+		if (!verify_directory(private.inpath))
+		{
+			fprintf(stderr,
+					"%s: --path %s is cannot be opened: %s",
+					progname, private.inpath, strerror(errno));
+			goto bad_argument;
+		}
+	}
+
+	/* parse files as start/end boundaries, extract path if not specified */
+	if (optind < argc)
+	{
+		char *directory = NULL;
+		char *fname = NULL;
+		int fd;
+		XLogSegNo segno;
+
+		split_path(argv[optind], &directory, &fname);
+
+		if (private.inpath == NULL && directory != NULL)
+		{
+			private.inpath = directory;
+
+			if (!verify_directory(private.inpath))
+				fatal_error("cannot open directory %s: %s",
+							private.inpath, strerror(errno));
+		}
+
+		fd = fuzzy_open_file(private.inpath, fname);
+		if (fd < 0)
+			fatal_error("could not open file %s", fname);
+		close(fd);
+
+		/* parse position from file */
+		XLogFromFileName(fname, &private.timeline, &segno);
+
+		if (XLogRecPtrIsInvalid(private.startptr))
+			XLogSegNoOffsetToRecPtr(segno, 0, private.startptr);
+		else if (!XLByteInSeg(private.startptr, segno))
+		{
+			fprintf(stderr,
+					"%s: --end %X/%X is not inside file \"%s\"\n",
+					progname,
+					(uint32)(private.startptr >> 32),
+					(uint32)private.startptr,
+					fname);
+			goto bad_argument;
+		}
+
+		/* no second file specified, set end position */
+		if (!(optind + 1 < argc) && XLogRecPtrIsInvalid(private.endptr))
+			XLogSegNoOffsetToRecPtr(segno + 1, 0, private.endptr);
+
+		/* parse ENDSEG if passed */
+		if (optind + 1 < argc)
+		{
+			XLogSegNo endsegno;
+
+			/* ignore directory, already have that */
+			split_path(argv[optind + 1], &directory, &fname);
+
+			fd = fuzzy_open_file(private.inpath, fname);
+			if (fd < 0)
+				fatal_error("could not open file %s", fname);
+			close(fd);
+
+			/* parse position from file */
+			XLogFromFileName(fname, &private.timeline, &endsegno);
+
+			if (endsegno < segno)
+				fatal_error("ENDSEG %s is before STARSEG %s",
+							argv[optind + 1], argv[optind]);
+
+			if (XLogRecPtrIsInvalid(private.endptr))
+				XLogSegNoOffsetToRecPtr(endsegno + 1, 0, private.endptr);
+
+			/* set segno to endsegno for check of --end */
+			segno = endsegno;
+		}
+
+
+		if (!XLByteInSeg(private.endptr, segno) &&
+			private.endptr != (segno + 1) * XLogSegSize)
+		{
+			fprintf(stderr,
+					"%s: --end %X/%X is not inside file \"%s\"\n",
+					progname,
+					(uint32)(private.endptr >> 32),
+					(uint32)private.endptr,
+					argv[argc -1]);
+			goto bad_argument;
+		}
+	}
+
+	/* we don't know what to print */
+	if (XLogRecPtrIsInvalid(private.startptr))
+	{
+		fprintf(stderr, "%s: no --start given in range mode.\n", progname);
+		goto bad_argument;
+	}
+
+	/* done with argument parsing, do the actual work */
+
+	/* we have everything we need, start reading */
+	xlogreader_state = XLogReaderAllocate(private.startptr,
+										  XLogDumpReadPage,
+										  &private);
+
+	/* first find a valid recptr to start from */
+	first_record = XLogFindNextRecord(xlogreader_state, private.startptr);
+
+	if (first_record == InvalidXLogRecPtr)
+		fatal_error("could not find a valid record after %X/%X",
+					(uint32) (private.startptr >> 32),
+					(uint32) private.startptr);
+
+	/*
+	 * Display a message that were skipping data if `from` wasn't a pointer
+	 * to the start of a record and also wasn't a pointer to the beginning
+	 * of a segment (e.g. we were used in file mode).
+	 */
+	if (first_record != private.startptr && (private.startptr % XLogSegSize) != 0)
+		printf("first record is after %X/%X, at %X/%X, skipping over %u bytes\n",
+			   (uint32) (private.startptr >> 32), (uint32) private.startptr,
+			   (uint32) (first_record >> 32), (uint32) first_record,
+			   (uint32) (first_record - private.startptr));
+
+	while ((record = XLogReadRecord(xlogreader_state, first_record, &errormsg)))
+	{
+		/* continue after the last record */
+		first_record = InvalidXLogRecPtr;
+		XLogDumpDisplayRecord(xlogreader_state, record);
+
+		/* check whether we printed enough */
+		if (private.stop_after_records > 0 &&
+			private.already_displayed_records >= private.stop_after_records)
+			break;
+	}
+
+	if (errormsg)
+		fatal_error("error in WAL record at %X/%X: %s\n",
+					(uint32)(xlogreader_state->ReadRecPtr >> 32),
+					(uint32)xlogreader_state->ReadRecPtr,
+					errormsg);
+
+	XLogReaderFree(xlogreader_state);
+
+	return EXIT_SUCCESS;
+bad_argument:
+	fprintf(stderr, "Try \"%s --help\" for more information.\n", progname);
+	return EXIT_FAILURE;
+}
diff --git a/contrib/pg_xlogdump/tables.c b/contrib/pg_xlogdump/tables.c
new file mode 100644
index 0000000..e947e0d
--- /dev/null
+++ b/contrib/pg_xlogdump/tables.c
@@ -0,0 +1,78 @@
+/*-------------------------------------------------------------------------
+ *
+ * tables.c
+ *		Support data for xlogdump.c
+ *
+ * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		contrib/pg_xlogdump/tables.c
+ *
+ * NOTES
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/*
+ * rmgr.c
+ *
+ * Resource managers definition
+ *
+ * src/backend/access/transam/rmgr.c
+ */
+#include "postgres.h"
+
+#include "access/clog.h"
+#include "access/gin.h"
+#include "access/gist_private.h"
+#include "access/hash.h"
+#include "access/heapam_xlog.h"
+#include "access/multixact.h"
+#include "access/nbtree.h"
+#include "access/spgist.h"
+#include "access/xact.h"
+#include "access/xlog_internal.h"
+#include "catalog/storage_xlog.h"
+#include "commands/dbcommands.h"
+#include "commands/sequence.h"
+#include "commands/tablespace.h"
+#include "storage/standby.h"
+#include "utils/relmapper.h"
+#include "catalog/catalog.h"
+
+/*
+ * Table of fork names.
+ *
+ * needs to be synced with src/backend/catalog/catalog.c
+ */
+const char *forkNames[] = {
+	"main",						/* MAIN_FORKNUM */
+	"fsm",						/* FSM_FORKNUM */
+	"vm",						/* VISIBILITYMAP_FORKNUM */
+	"init"						/* INIT_FORKNUM */
+};
+
+/*
+ * RmgrTable linked only to functions available outside of the backend.
+ *
+ * needs to be synced with src/backend/access/transam/rmgr.c
+ */
+const RmgrData RmgrTable[RM_MAX_ID + 1] = {
+	{"XLOG", NULL, xlog_desc, NULL, NULL, NULL},
+	{"Transaction", NULL, xact_desc, NULL, NULL, NULL},
+	{"Storage", NULL, smgr_desc, NULL, NULL, NULL},
+	{"CLOG", NULL, clog_desc, NULL, NULL, NULL},
+	{"Database", NULL, dbase_desc, NULL, NULL, NULL},
+	{"Tablespace", NULL, tblspc_desc, NULL, NULL, NULL},
+	{"MultiXact", NULL, multixact_desc, NULL, NULL, NULL},
+	{"RelMap", NULL, relmap_desc, NULL, NULL, NULL},
+	{"Standby", NULL, standby_desc, NULL, NULL, NULL},
+	{"Heap2", NULL, heap2_desc, NULL, NULL, NULL},
+	{"Heap", NULL, heap_desc, NULL, NULL, NULL},
+	{"Btree", NULL, btree_desc, NULL, NULL, NULL},
+	{"Hash", NULL, hash_desc, NULL, NULL, NULL},
+	{"Gin", NULL, gin_desc, NULL, NULL, NULL},
+	{"Gist", NULL, gist_desc, NULL, NULL, NULL},
+	{"Sequence", NULL, seq_desc, NULL, NULL, NULL},
+	{"SPGist", NULL, spg_desc, NULL, NULL, NULL}
+};
diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index df84054..49cb7ac 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -178,6 +178,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY pgReceivexlog      SYSTEM "pg_receivexlog.sgml">
 <!ENTITY pgResetxlog        SYSTEM "pg_resetxlog.sgml">
 <!ENTITY pgRestore          SYSTEM "pg_restore.sgml">
+<!ENTITY pgXlogdump         SYSTEM "pg_xlogdump.sgml">
 <!ENTITY postgres           SYSTEM "postgres-ref.sgml">
 <!ENTITY postmaster         SYSTEM "postmaster.sgml">
 <!ENTITY psqlRef            SYSTEM "psql-ref.sgml">
diff --git a/doc/src/sgml/ref/pg_xlogdump.sgml b/doc/src/sgml/ref/pg_xlogdump.sgml
new file mode 100644
index 0000000..7a27c7b
--- /dev/null
+++ b/doc/src/sgml/ref/pg_xlogdump.sgml
@@ -0,0 +1,76 @@
+<!--
+doc/src/sgml/ref/pg_xlogdump.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="APP-PGXLOGDUMP">
+ <refmeta>
+  <refentrytitle><application>pg_xlogdump</application></refentrytitle>
+  <manvolnum>1</manvolnum>
+  <refmiscinfo>Application</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>pg_xlogdump</refname>
+  <refpurpose>Display the write-ahead log of a <productname>PostgreSQL</productname> database cluster</refpurpose>
+ </refnamediv>
+
+ <indexterm zone="app-pgxlogdump">
+  <primary>pg_xlogdump</primary>
+ </indexterm>
+
+ <refsynopsisdiv>
+  <cmdsynopsis>
+   <command>pg_xlogdump</command>
+   <arg choice="opt"><option>-b</option></arg>
+   <arg choice="opt"><option>-e</option> <replaceable class="parameter">xlogrecptr</replaceable></arg>
+   <arg choice="opt"><option>-f</option> <replaceable class="parameter">filename</replaceable></arg>
+   <arg choice="opt"><option>-h</option></arg>
+   <arg choice="opt"><option>-p</option> <replaceable class="parameter">directory</replaceable></arg>
+   <arg choice="opt"><option>-s</option> <replaceable class="parameter">xlogrecptr</replaceable></arg>
+   <arg choice="opt"><option>-t</option> <replaceable class="parameter">timelineid</replaceable></arg>
+   <arg choice="opt"><option>-v</option></arg>
+  </cmdsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1 id="R1-APP-PGXLOGDUMP-1">
+  <title>Description</title>
+  <para>
+   <command>pg_xlogdump</command> display the write-ahead log (WAL) and is only
+   useful for debugging or educational purposes.
+  </para>
+
+  <para>
+   This utility can only be run by the user who installed the server, because
+   it requires read access to the data directory. It does not perform any
+   modifications.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Options</title>
+
+   <para>
+    The following command-line options control the location and format of the
+    output.
+
+    <variablelist>
+     <varlistentry>
+      <term><option>-p <replaceable class="parameter">directory</replaceable></option></term>
+      <listitem>
+       <para>
+        Directory to find xlog files in.
+       </para>
+      </listitem>
+     </varlistentry>
+    </variablelist>
+   </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Notes</title>
+  <para>
+    Can give wrong results when the server is running.
+  </para>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index 0872168..fed1fdd 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -225,6 +225,7 @@
    &pgDumpall;
    &pgReceivexlog;
    &pgRestore;
+   &pgXlogdump;
    &psqlRef;
    &reindexdb;
    &vacuumdb;
diff --git a/src/backend/access/transam/rmgr.c b/src/backend/access/transam/rmgr.c
index cc210a7..4e94af1 100644
--- a/src/backend/access/transam/rmgr.c
+++ b/src/backend/access/transam/rmgr.c
@@ -24,6 +24,7 @@
 #include "storage/standby.h"
 #include "utils/relmapper.h"
 
+/* Also update contrib/pg_xlogdump/tables.c if you add something here. */
 
 const RmgrData RmgrTable[RM_MAX_ID + 1] = {
 	{"XLOG", xlog_redo, xlog_desc, NULL, NULL, NULL},
diff --git a/src/backend/catalog/catalog.c b/src/backend/catalog/catalog.c
index 6455ef0..92ab3ca 100644
--- a/src/backend/catalog/catalog.c
+++ b/src/backend/catalog/catalog.c
@@ -52,6 +52,8 @@
  * If you add a new entry, remember to update the errhint below, and the
  * documentation for pg_relation_size(). Also keep FORKNAMECHARS above
  * up-to-date.
+ *
+ * Also update contrib/pg_xlogdump/tables.c if you add something here.
  */
 const char *forkNames[] = {
 	"main",						/* MAIN_FORKNUM */
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index d587365..7b6ed41 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -41,7 +41,7 @@ my $contrib_extraincludes =
 my $contrib_extrasource = {
 	'cube' => [ 'cubescan.l', 'cubeparse.y' ],
 	'seg'  => [ 'segscan.l',  'segparse.y' ] };
-my @contrib_excludes = ('pgcrypto', 'intagg', 'sepgsql');
+my @contrib_excludes = ('intagg', 'pgcrypto', 'pg_xlogdump', 'sepgsql');
 
 sub mkvcbuild
 {
@@ -409,6 +409,20 @@ sub mkvcbuild
 		'localtime.c');
 	$zic->AddReference($libpgport);
 
+	my $pgxlogdump = $solution->AddProject('pg_xlogdump', 'exe', 'contrib');
+	$pgxlogdump->{name} = 'pg_xlogdump';
+	$pgxlogdump->AddIncludeDir('src\backend');
+	$pgxlogdump->AddFiles('contrib\pg_xlogdump',
+		'compat.c', 'pg_xlogdump.c', 'tables.c');
+	$pgxlogdump->AddFile('src\backend\access\transam\xlogreader.c');
+	$pgxlogdump->AddFiles('src\backend\access\rmgrdesc',
+		'clogdesc.c', 'dbasedesc.c', 'gindesc.c', 'gistdesc.c', 'hashdesc.c',
+		'heapdesc.c', 'mxactdesc.c', 'nbtdesc.c', 'relmapdesc.c', 'seqdesc.c',
+		'smgrdesc.c', 'spgdesc.c', 'standbydesc.c', 'tblspcdesc.c',
+		'xactdesc.c', 'xlogdesc.c');
+	$pgxlogdump->AddReference($libpgport);
+	$pgxlogdump->AddDefine('FRONTEND');
+
 	if ($solution->{options}->{xml})
 	{
 		$contrib_extraincludes->{'pgxml'} = [
-- 
1.7.12.289.g0ce9864.dirty



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