Add contrib/pg_walinspect.

Provides similar functionality to pg_waldump, but from a SQL interface
rather than a separate utility.

Author: Bharath Rupireddy
Reviewed-by: Greg Stark, Kyotaro Horiguchi, Andres Freund, Ashutosh Sharma, Nitin Jadhav, RKN Sai Krishna
Discussion: https://postgr.es/m/CALj2ACUGUYXsEQdKhEdsBzhGEyF3xggvLdD8C0VT72TNEfOiog%40mail.gmail.com

13 files changed, 332 insertions, 203 deletions

diff --git a/src/backend/access/rmgrdesc/xlogdesc.c b/src/backend/access/rmgrdesc/xlogdesc.c
index e7452af6790..dff1e7685e9 100644
--- a/src/backend/access/rmgrdesc/xlogdesc.c
+++ b/src/backend/access/rmgrdesc/xlogdesc.c
@@ -200,3 +200,133 @@ xlog_identify(uint8 info)
 
 	return id;
 }
+
+/*
+ * Returns a string giving information about all the blocks in an
+ * XLogRecord.
+ */
+void
+XLogRecGetBlockRefInfo(XLogReaderState *record, bool pretty,
+					   bool detailed_format, StringInfo buf,
+					   uint32 *fpi_len)
+{
+	int	block_id;
+
+	Assert(record != NULL);
+
+	if (detailed_format && pretty)
+		appendStringInfoChar(buf, '\n');
+
+	for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
+	{
+		RelFileNode rnode = {InvalidOid, InvalidOid, InvalidOid};
+		ForkNumber	forknum = InvalidForkNumber;
+		BlockNumber blk = InvalidBlockNumber;
+
+		if (!XLogRecHasBlockRef(record, block_id))
+			continue;
+
+		XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blk);
+
+		if (detailed_format)
+		{
+			/* Get block references in detailed format. */
+
+			if (pretty)
+				appendStringInfoChar(buf, '\t');
+			else if (block_id > 0)
+				appendStringInfoChar(buf, ' ');
+
+			appendStringInfo(buf,
+							 "blkref #%d: rel %u/%u/%u fork %s blk %u",
+							 block_id,
+							 rnode.spcNode, rnode.dbNode, rnode.relNode,
+							 forkNames[forknum],
+							 blk);
+
+			if (XLogRecHasBlockImage(record, block_id))
+			{
+				uint8		bimg_info = XLogRecGetBlock(record, block_id)->bimg_info;
+
+				/* Calculate the amount of FPI data in the record. */
+				if (fpi_len)
+					*fpi_len += XLogRecGetBlock(record, block_id)->bimg_len;
+
+				if (BKPIMAGE_COMPRESSED(bimg_info))
+				{
+					const char *method;
+
+					if ((bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
+						method = "pglz";
+					else if ((bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
+						method = "lz4";
+					else if ((bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
+						method = "zstd";
+					else
+						method = "unknown";
+
+					appendStringInfo(buf,
+									 " (FPW%s); hole: offset: %u, length: %u, "
+									 "compression saved: %u, method: %s",
+									 XLogRecBlockImageApply(record, block_id) ?
+									 "" : " for WAL verification",
+									 XLogRecGetBlock(record, block_id)->hole_offset,
+									 XLogRecGetBlock(record, block_id)->hole_length,
+									 BLCKSZ -
+									 XLogRecGetBlock(record, block_id)->hole_length -
+									 XLogRecGetBlock(record, block_id)->bimg_len,
+									 method);
+				}
+				else
+				{
+					appendStringInfo(buf,
+									 " (FPW%s); hole: offset: %u, length: %u",
+									 XLogRecBlockImageApply(record, block_id) ?
+									 "" : " for WAL verification",
+									 XLogRecGetBlock(record, block_id)->hole_offset,
+									 XLogRecGetBlock(record, block_id)->hole_length);
+				}
+			}
+
+			if (pretty)
+				appendStringInfoChar(buf, '\n');
+		}
+		else
+		{
+			/* Get block references in short format. */
+
+			if (forknum != MAIN_FORKNUM)
+			{
+				appendStringInfo(buf,
+								 ", blkref #%d: rel %u/%u/%u fork %s blk %u",
+								 block_id,
+								 rnode.spcNode, rnode.dbNode, rnode.relNode,
+								 forkNames[forknum],
+								 blk);
+			}
+			else
+			{
+				appendStringInfo(buf,
+								 ", blkref #%d: rel %u/%u/%u blk %u",
+								 block_id,
+								 rnode.spcNode, rnode.dbNode, rnode.relNode,
+								 blk);
+			}
+
+			if (XLogRecHasBlockImage(record, block_id))
+			{
+				/* Calculate the amount of FPI data in the record. */
+				if (fpi_len)
+					*fpi_len += XLogRecGetBlock(record, block_id)->bimg_len;
+
+				if (XLogRecBlockImageApply(record, block_id))
+					appendStringInfo(buf, " FPW");
+				else
+					appendStringInfo(buf, " FPW for WAL verification");
+			}
+		}
+	}
+
+	if (!detailed_format && pretty)
+		appendStringInfoChar(buf, '\n');
+}
diff --git a/src/backend/access/transam/Makefile b/src/backend/access/transam/Makefile
index 8c17c88dfc4..3e5444a6f76 100644
--- a/src/backend/access/transam/Makefile
+++ b/src/backend/access/transam/Makefile
@@ -34,6 +34,7 @@ OBJS = \
 	xlogprefetcher.o \
 	xlogreader.o \
 	xlogrecovery.o \
+	xlogstats.o \
 	xlogutils.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 5862d9dc75f..a5f1a648d3d 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -1320,13 +1320,6 @@ XLogReaderValidatePageHeader(XLogReaderState *state, XLogRecPtr recptr,
 	return true;
 }
 
-#ifdef FRONTEND
-/*
- * Functions that are currently not needed in the backend, but are better
- * implemented inside xlogreader.c because of the internal facilities available
- * here.
- */
-
 /*
  * Find the first record with an lsn >= RecPtr.
  *
@@ -1447,8 +1440,6 @@ err:
 	return InvalidXLogRecPtr;
 }
 
-#endif							/* FRONTEND */
-
 /*
  * Helper function to ease writing of XLogRoutine->page_read callbacks.
  * If this function is used, caller must supply a segment_open callback in
diff --git a/src/backend/access/transam/xlogstats.c b/src/backend/access/transam/xlogstats.c
new file mode 100644
index 00000000000..aff3069ecba
--- /dev/null
+++ b/src/backend/access/transam/xlogstats.c
@@ -0,0 +1,93 @@
+/*-------------------------------------------------------------------------
+ *
+ * xlogstats.c
+ *		Functions for WAL Statitstics
+ *
+ * Copyright (c) 2022, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		src/backend/access/transam/xlogstats.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/xlogreader.h"
+#include "access/xlogstats.h"
+
+/*
+ * Calculate the size of a record, split into !FPI and FPI parts.
+ */
+void
+XLogRecGetLen(XLogReaderState *record, uint32 *rec_len,
+			  uint32 *fpi_len)
+{
+	int	block_id;
+
+	/*
+	 * Calculate the amount of FPI data in the record.
+	 *
+	 * XXX: We peek into xlogreader's private decoded backup blocks for the
+	 * bimg_len indicating the length of FPI data.
+	 */
+	*fpi_len = 0;
+	for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
+	{
+		if (XLogRecHasBlockImage(record, block_id))
+			*fpi_len += XLogRecGetBlock(record, block_id)->bimg_len;
+	}
+
+	/*
+	 * Calculate the length of the record as the total length - the length of
+	 * all the block images.
+	 */
+	*rec_len = XLogRecGetTotalLen(record) - *fpi_len;
+}
+
+/*
+ * Store per-rmgr and per-record statistics for a given record.
+ */
+void
+XLogRecStoreStats(XLogStats *stats, XLogReaderState *record)
+{
+	RmgrId	rmid;
+	uint8	recid;
+	uint32	rec_len;
+	uint32	fpi_len;
+
+	Assert(stats != NULL && record != NULL);
+
+	stats->count++;
+
+	rmid = XLogRecGetRmid(record);
+
+	XLogRecGetLen(record, &rec_len, &fpi_len);
+
+	/* Update per-rmgr statistics */
+
+	stats->rmgr_stats[rmid].count++;
+	stats->rmgr_stats[rmid].rec_len += rec_len;
+	stats->rmgr_stats[rmid].fpi_len += fpi_len;
+
+	/*
+	 * Update per-record statistics, where the record is identified by a
+	 * combination of the RmgrId and the four bits of the xl_info field that
+	 * are the rmgr's domain (resulting in sixteen possible entries per
+	 * RmgrId).
+	 */
+
+	recid = XLogRecGetInfo(record) >> 4;
+
+	/*
+	 * XACT records need to be handled differently. Those records use the
+	 * first bit of those four bits for an optional flag variable and the
+	 * following three bits for the opcode. We filter opcode out of xl_info
+	 * and use it as the identifier of the record.
+	 */
+	if (rmid == RM_XACT_ID)
+		recid &= 0x07;
+
+	stats->record_stats[rmid][recid].count++;
+	stats->record_stats[rmid][recid].rec_len += rec_len;
+	stats->record_stats[rmid][recid].fpi_len += fpi_len;
+}
diff --git a/src/backend/access/transam/xlogutils.c b/src/backend/access/transam/xlogutils.c
index bb2d3ec991c..b5d34c61e66 100644
--- a/src/backend/access/transam/xlogutils.c
+++ b/src/backend/access/transam/xlogutils.c
@@ -80,6 +80,10 @@ typedef struct xl_invalid_page
 
 static HTAB *invalid_page_tab = NULL;
 
+static int
+read_local_xlog_page_guts(XLogReaderState *state, XLogRecPtr targetPagePtr,
+						  int reqLen, XLogRecPtr targetRecPtr,
+						  char *cur_page, bool wait_for_wal);
 
 /* Report a reference to an invalid page */
 static void
@@ -871,6 +875,31 @@ int
 read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
 					 int reqLen, XLogRecPtr targetRecPtr, char *cur_page)
 {
+	return read_local_xlog_page_guts(state, targetPagePtr, reqLen,
+									 targetRecPtr, cur_page, true);
+}
+
+/*
+ * Same as read_local_xlog_page except that it doesn't wait for future WAL
+ * to be available.
+ */
+int
+read_local_xlog_page_no_wait(XLogReaderState *state, XLogRecPtr targetPagePtr,
+							 int reqLen, XLogRecPtr targetRecPtr,
+							 char *cur_page)
+{
+	return read_local_xlog_page_guts(state, targetPagePtr, reqLen,
+									 targetRecPtr, cur_page, false);
+}
+
+/*
+ * Implementation of read_local_xlog_page and its no wait version.
+ */
+static int
+read_local_xlog_page_guts(XLogReaderState *state, XLogRecPtr targetPagePtr,
+						  int reqLen, XLogRecPtr targetRecPtr,
+						  char *cur_page, bool wait_for_wal)
+{
 	XLogRecPtr	read_upto,
 				loc;
 	TimeLineID	tli;
@@ -925,6 +954,10 @@ read_local_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr,
 			if (loc <= read_upto)
 				break;
 
+			/* If asked, let's not wait for future WAL. */
+			if (!wait_for_wal)
+				break;
+
 			CHECK_FOR_INTERRUPTS();
 			pg_usleep(1000L);
 		}
diff --git a/src/bin/pg_waldump/.gitignore b/src/bin/pg_waldump/.gitignore
index 3be00a8b61f..dabb6e34b6f 100644
--- a/src/bin/pg_waldump/.gitignore
+++ b/src/bin/pg_waldump/.gitignore
@@ -23,6 +23,7 @@
 /xactdesc.c
 /xlogdesc.c
 /xlogreader.c
+/xlogstat.c
 
 # Generated by test suite
 /tmp_check/
diff --git a/src/bin/pg_waldump/Makefile b/src/bin/pg_waldump/Makefile
index 9f333d0c8ab..d6459e17c73 100644
--- a/src/bin/pg_waldump/Makefile
+++ b/src/bin/pg_waldump/Makefile
@@ -13,7 +13,8 @@ OBJS = \
 	compat.o \
 	pg_waldump.o \
 	rmgrdesc.o \
-	xlogreader.o
+	xlogreader.o \
+	xlogstats.o
 
 override CPPFLAGS := -DFRONTEND $(CPPFLAGS)
 
@@ -29,6 +30,9 @@ pg_waldump: $(OBJS) | submake-libpgport
 xlogreader.c: % : $(top_srcdir)/src/backend/access/transam/%
 	rm -f $@ && $(LN_S) $< .
 
+xlogstats.c: % : $(top_srcdir)/src/backend/access/transam/%
+	rm -f $@ && $(LN_S) $< .
+
 $(RMGRDESCSOURCES): % : $(top_srcdir)/src/backend/access/rmgrdesc/%
 	rm -f $@ && $(LN_S) $< .
 
@@ -42,7 +46,7 @@ uninstall:
 	rm -f '$(DESTDIR)$(bindir)/pg_waldump$(X)'
 
 clean distclean maintainer-clean:
-	rm -f pg_waldump$(X) $(OBJS) $(RMGRDESCSOURCES) xlogreader.c
+	rm -f pg_waldump$(X) $(OBJS) $(RMGRDESCSOURCES) xlogreader.c xlogstats.c
 	rm -rf tmp_check
 
 check:
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index 30ca7684bd0..8bf6899d678 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -21,11 +21,17 @@
 #include "access/xlog_internal.h"
 #include "access/xlogreader.h"
 #include "access/xlogrecord.h"
+#include "access/xlogstats.h"
 #include "common/fe_memutils.h"
 #include "common/logging.h"
 #include "getopt_long.h"
 #include "rmgrdesc.h"
 
+/*
+ * NOTE: For any code change or issue fix here, it is highly recommended to
+ * give a thought about doing the same in pg_walinspect contrib module as well.
+ */
+
 static const char *progname;
 
 static int	WalSegSz;
@@ -66,24 +72,6 @@ typedef struct XLogDumpConfig
 	bool		filter_by_fpw;
 } XLogDumpConfig;
 
-typedef struct Stats
-{
-	uint64		count;
-	uint64		rec_len;
-	uint64		fpi_len;
-} Stats;
-
-#define MAX_XLINFO_TYPES 16
-
-typedef struct XLogDumpStats
-{
-	uint64		count;
-	XLogRecPtr	startptr;
-	XLogRecPtr	endptr;
-	Stats		rmgr_stats[RM_MAX_ID + 1];
-	Stats		record_stats[RM_MAX_ID + 1][MAX_XLINFO_TYPES];
-} XLogDumpStats;
-
 #define fatal_error(...) do { pg_log_fatal(__VA_ARGS__); exit(EXIT_FAILURE); } while(0)
 
 /*
@@ -454,81 +442,6 @@ XLogRecordHasFPW(XLogReaderState *record)
 }
 
 /*
- * Calculate the size of a record, split into !FPI and FPI parts.
- */
-static void
-XLogDumpRecordLen(XLogReaderState *record, uint32 *rec_len, uint32 *fpi_len)
-{
-	int			block_id;
-
-	/*
-	 * Calculate the amount of FPI data in the record.
-	 *
-	 * XXX: We peek into xlogreader's private decoded backup blocks for the
-	 * bimg_len indicating the length of FPI data.
-	 */
-	*fpi_len = 0;
-	for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
-	{
-		if (XLogRecHasBlockImage(record, block_id))
-			*fpi_len += XLogRecGetBlock(record, block_id)->bimg_len;
-	}
-
-	/*
-	 * Calculate the length of the record as the total length - the length of
-	 * all the block images.
-	 */
-	*rec_len = XLogRecGetTotalLen(record) - *fpi_len;
-}
-
-/*
- * Store per-rmgr and per-record statistics for a given record.
- */
-static void
-XLogDumpCountRecord(XLogDumpConfig *config, XLogDumpStats *stats,
-					XLogReaderState *record)
-{
-	RmgrId		rmid;
-	uint8		recid;
-	uint32		rec_len;
-	uint32		fpi_len;
-
-	stats->count++;
-
-	rmid = XLogRecGetRmid(record);
-
-	XLogDumpRecordLen(record, &rec_len, &fpi_len);
-
-	/* Update per-rmgr statistics */
-
-	stats->rmgr_stats[rmid].count++;
-	stats->rmgr_stats[rmid].rec_len += rec_len;
-	stats->rmgr_stats[rmid].fpi_len += fpi_len;
-
-	/*
-	 * Update per-record statistics, where the record is identified by a
-	 * combination of the RmgrId and the four bits of the xl_info field that
-	 * are the rmgr's domain (resulting in sixteen possible entries per
-	 * RmgrId).
-	 */
-
-	recid = XLogRecGetInfo(record) >> 4;
-
-	/*
-	 * XACT records need to be handled differently. Those records use the
-	 * first bit of those four bits for an optional flag variable and the
-	 * following three bits for the opcode. We filter opcode out of xl_info
-	 * and use it as the identifier of the record.
-	 */
-	if (rmid == RM_XACT_ID)
-		recid &= 0x07;
-
-	stats->record_stats[rmid][recid].count++;
-	stats->record_stats[rmid][recid].rec_len += rec_len;
-	stats->record_stats[rmid][recid].fpi_len += fpi_len;
-}
-
-/*
  * Print a record to stdout
  */
 static void
@@ -538,15 +451,11 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
 	const RmgrDescData *desc = GetRmgrDesc(XLogRecGetRmid(record));
 	uint32		rec_len;
 	uint32		fpi_len;
-	RelFileNode rnode;
-	ForkNumber	forknum;
-	BlockNumber blk;
-	int			block_id;
 	uint8		info = XLogRecGetInfo(record);
 	XLogRecPtr	xl_prev = XLogRecGetPrev(record);
 	StringInfoData s;
 
-	XLogDumpRecordLen(record, &rec_len, &fpi_len);
+	XLogRecGetLen(record, &rec_len, &fpi_len);
 
 	printf("rmgr: %-11s len (rec/tot): %6u/%6u, tx: %10u, lsn: %X/%08X, prev %X/%08X, ",
 		   desc->rm_name,
@@ -564,93 +473,11 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
 	initStringInfo(&s);
 	desc->rm_desc(&s, record);
 	printf("%s", s.data);
-	pfree(s.data);
-
-	if (!config->bkp_details)
-	{
-		/* print block references (short format) */
-		for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
-		{
-			if (!XLogRecHasBlockRef(record, block_id))
-				continue;
-
-			XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blk);
-			if (forknum != MAIN_FORKNUM)
-				printf(", blkref #%d: rel %u/%u/%u fork %s blk %u",
-					   block_id,
-					   rnode.spcNode, rnode.dbNode, rnode.relNode,
-					   forkNames[forknum],
-					   blk);
-			else
-				printf(", blkref #%d: rel %u/%u/%u blk %u",
-					   block_id,
-					   rnode.spcNode, rnode.dbNode, rnode.relNode,
-					   blk);
-			if (XLogRecHasBlockImage(record, block_id))
-			{
-				if (XLogRecBlockImageApply(record, block_id))
-					printf(" FPW");
-				else
-					printf(" FPW for WAL verification");
-			}
-		}
-		putchar('\n');
-	}
-	else
-	{
-		/* print block references (detailed format) */
-		putchar('\n');
-		for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
-		{
-			if (!XLogRecHasBlockRef(record, block_id))
-				continue;
-
-			XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blk);
-			printf("\tblkref #%d: rel %u/%u/%u fork %s blk %u",
-				   block_id,
-				   rnode.spcNode, rnode.dbNode, rnode.relNode,
-				   forkNames[forknum],
-				   blk);
-			if (XLogRecHasBlockImage(record, block_id))
-			{
-				uint8		bimg_info = XLogRecGetBlock(record, block_id)->bimg_info;
 
-				if (BKPIMAGE_COMPRESSED(bimg_info))
-				{
-					const char *method;
-
-					if ((bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
-						method = "pglz";
-					else if ((bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
-						method = "lz4";
-					else if ((bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
-						method = "zstd";
-					else
-						method = "unknown";
-
-					printf(" (FPW%s); hole: offset: %u, length: %u, "
-						   "compression saved: %u, method: %s",
-						   XLogRecBlockImageApply(record, block_id) ?
-						   "" : " for WAL verification",
-						   XLogRecGetBlock(record, block_id)->hole_offset,
-						   XLogRecGetBlock(record, block_id)->hole_length,
-						   BLCKSZ -
-						   XLogRecGetBlock(record, block_id)->hole_length -
-						   XLogRecGetBlock(record, block_id)->bimg_len,
-						   method);
-				}
-				else
-				{
-					printf(" (FPW%s); hole: offset: %u, length: %u",
-						   XLogRecBlockImageApply(record, block_id) ?
-						   "" : " for WAL verification",
-						   XLogRecGetBlock(record, block_id)->hole_offset,
-						   XLogRecGetBlock(record, block_id)->hole_length);
-				}
-			}
-			putchar('\n');
-		}
-	}
+	resetStringInfo(&s);
+	XLogRecGetBlockRefInfo(record, true, config->bkp_details, &s, NULL);
+	printf("%s", s.data);
+	pfree(s.data);
 }
 
 /*
@@ -698,7 +525,7 @@ XLogDumpStatsRow(const char *name,
  * Display summary statistics about the records seen so far.
  */
 static void
-XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
+XLogDumpDisplayStats(XLogDumpConfig *config, XLogStats *stats)
 {
 	int			ri,
 				rj;
@@ -722,6 +549,9 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
 
 	for (ri = 0; ri <= RM_MAX_ID; ri++)
 	{
+		if (!RmgrIdIsValid(ri))
+			continue;
+
 		total_count += stats->rmgr_stats[ri].count;
 		total_rec_len += stats->rmgr_stats[ri].rec_len;
 		total_fpi_len += stats->rmgr_stats[ri].fpi_len;
@@ -867,7 +697,7 @@ main(int argc, char **argv)
 	XLogReaderState *xlogreader_state;
 	XLogDumpPrivate private;
 	XLogDumpConfig config;
-	XLogDumpStats stats;
+	XLogStats stats;
 	XLogRecord *record;
 	XLogRecPtr	first_record;
 	char	   *waldir = NULL;
@@ -921,7 +751,7 @@ main(int argc, char **argv)
 
 	memset(&private, 0, sizeof(XLogDumpPrivate));
 	memset(&config, 0, sizeof(XLogDumpConfig));
-	memset(&stats, 0, sizeof(XLogDumpStats));
+	memset(&stats, 0, sizeof(XLogStats));
 
 	private.timeline = 1;
 	private.startptr = InvalidXLogRecPtr;
@@ -1319,7 +1149,7 @@ main(int argc, char **argv)
 		{
 			if (config.stats == true)
 			{
-				XLogDumpCountRecord(&config, &stats, xlogreader_state);
+				XLogRecStoreStats(&stats, xlogreader_state);
 				stats.endptr = xlogreader_state->EndRecPtr;
 			}
 			else
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index e302bd102cd..5e1e3446aed 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -31,7 +31,7 @@ extern XLogRecPtr XactLastRecEnd;
 extern PGDLLIMPORT XLogRecPtr XactLastCommitEnd;
 
 /* these variables are GUC parameters related to XLOG */
-extern int	wal_segment_size;
+extern PGDLLIMPORT int	wal_segment_size;
 extern int	min_wal_size_mb;
 extern int	max_wal_size_mb;
 extern int	wal_keep_size_mb;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index d9df7f295d5..750f6341205 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -320,7 +320,7 @@ typedef struct RmgrData
 							  struct XLogRecordBuffer *buf);
 } RmgrData;
 
-extern RmgrData RmgrTable[];
+extern PGDLLIMPORT RmgrData RmgrTable[];
 extern void RmgrStartup(void);
 extern void RmgrCleanup(void);
 extern void RmgrNotFound(RmgrId rmid);
@@ -350,6 +350,10 @@ extern XLogRecPtr RequestXLogSwitch(bool mark_unimportant);
 
 extern void GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli);
 
+extern void XLogRecGetBlockRefInfo(XLogReaderState *record, bool pretty,
+								   bool detailed_format, StringInfo buf,
+								   uint32 *fpi_len);
+
 /*
  * Exported for the functions in timeline.c and xlogarchive.c.  Only valid
  * in the startup process.
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
index d8eb8576110..727e9fe9718 100644
--- a/src/include/access/xlogreader.h
+++ b/src/include/access/xlogreader.h
@@ -344,9 +344,7 @@ extern void XLogReaderSetDecodeBuffer(XLogReaderState *state,
 
 /* Position the XLogReader to given record */
 extern void XLogBeginRead(XLogReaderState *state, XLogRecPtr RecPtr);
-#ifdef FRONTEND
 extern XLogRecPtr XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr);
-#endif							/* FRONTEND */
 
 /* Return values from XLogPageReadCB. */
 typedef enum XLogPageReadResult
diff --git a/src/include/access/xlogstats.h b/src/include/access/xlogstats.h
new file mode 100644
index 00000000000..453bb1f4913
--- /dev/null
+++ b/src/include/access/xlogstats.h
@@ -0,0 +1,40 @@
+/*-------------------------------------------------------------------------
+ *
+ * xlogstats.h
+ *		Definitions for WAL Statitstics
+ *
+ * Copyright (c) 2022, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		src/include/access/xlogstats.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef XLOGSTATS_H
+#define XLOGSTATS_H
+
+#define MAX_XLINFO_TYPES 16
+
+typedef struct XLogRecStats
+{
+	uint64	count;
+	uint64	rec_len;
+	uint64	fpi_len;
+} XLogRecStats;
+
+typedef struct XLogStats
+{
+	uint64	count;
+#ifdef FRONTEND
+	XLogRecPtr	startptr;
+	XLogRecPtr	endptr;
+#endif
+	XLogRecStats    rmgr_stats[RM_MAX_ID + 1];
+	XLogRecStats    record_stats[RM_MAX_ID + 1][MAX_XLINFO_TYPES];
+} XLogStats;
+
+extern void XLogRecGetLen(XLogReaderState *record, uint32 *rec_len,
+						  uint32 *fpi_len);
+extern void XLogRecStoreStats(XLogStats *stats, XLogReaderState *record);
+
+#endif							/* XLOGSTATS_H */
diff --git a/src/include/access/xlogutils.h b/src/include/access/xlogutils.h
index ff40f96e423..3746e31e40f 100644
--- a/src/include/access/xlogutils.h
+++ b/src/include/access/xlogutils.h
@@ -93,6 +93,10 @@ extern void FreeFakeRelcacheEntry(Relation fakerel);
 extern int	read_local_xlog_page(XLogReaderState *state,
 								 XLogRecPtr targetPagePtr, int reqLen,
 								 XLogRecPtr targetRecPtr, char *cur_page);
+extern int	read_local_xlog_page_no_wait(XLogReaderState *state,
+										 XLogRecPtr targetPagePtr, int reqLen,
+										 XLogRecPtr targetRecPtr,
+										 char *cur_page);
 extern void wal_segment_open(XLogReaderState *state,
 							 XLogSegNo nextSegNo,
 							 TimeLineID *tli_p);