fix_waldump_size_for_wal_switch_v3.patch

diff --git a/src/backend/access/rmgrdesc/xlogdesc.c b/src/backend/access/rmgrdesc/xlogdesc.c
index 3200f777f5..9aee7279a4 100644
--- a/src/backend/access/rmgrdesc/xlogdesc.c
+++ b/src/backend/access/rmgrdesc/xlogdesc.c
@@ -74,6 +74,13 @@ xlog_desc(StringInfo buf, XLogReaderState *record)
 		memcpy(&nextOid, rec, sizeof(Oid));
 		appendStringInfo(buf, "%u", nextOid);
 	}
+	else if (info == XLOG_SWITCH)
+	{
+		uint32	junk_len;
+		junk_len = xlog_switch_junk_len(record);
+
+		appendStringInfo(buf, "trailing-bytes: %u", junk_len);
+	}
 	else if (info == XLOG_RESTORE_POINT)
 	{
 		xl_restore_point *xlrec = (xl_restore_point *) rec;
@@ -142,6 +149,30 @@ xlog_desc(StringInfo buf, XLogReaderState *record)
 	}
 }
 
+uint32
+xlog_switch_junk_len(XLogReaderState *record)
+{
+	uint32 		junk_len;
+	XLogSegNo	startSegNo;
+	XLogSegNo	endSegNo;
+
+	XLByteToSeg(record->ReadRecPtr, startSegNo, record->segcxt.ws_segsize);
+	XLByteToSeg(record->EndRecPtr - 1, endSegNo, record->segcxt.ws_segsize);
+
+	junk_len = record->EndRecPtr - record->ReadRecPtr - XLogRecGetTotalLen(record);
+	/*
+	 * If the wal switch record spread on two segments, we should extra minus the
+	 * long page head. I mean the case when the remain size of a wal segment can not
+	 * afford a XLogRecord struct for XLOG_SWITCH.
+	 */
+	if(startSegNo != endSegNo)
+		junk_len -= SizeOfXLogLongPHD;
+
+	Assert(junk_len >= 0);
+
+	return junk_len;
+}
+
 const char *
 xlog_identify(uint8 info)
 {
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index 31e99c2a6d..0df4ddcf72 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -24,6 +24,7 @@
 #include "common/logging.h"
 #include "getopt_long.h"
 #include "rmgrdesc.h"
+#include "catalog/pg_control.h"
 
 static const char *progname;
 
@@ -66,6 +67,8 @@ typedef struct Stats
 typedef struct XLogDumpStats
 {
 	uint64		count;
+	uint64		count_xlog_switch;
+	uint32		junk_size;
 	Stats		rmgr_stats[RM_NEXT_ID];
 	Stats		record_stats[RM_NEXT_ID][MAX_XLINFO_TYPES];
 } XLogDumpStats;
@@ -416,12 +419,21 @@ XLogDumpCountRecord(XLogDumpConfig *config, XLogDumpStats *stats,
 	uint8		recid;
 	uint32		rec_len;
 	uint32		fpi_len;
+	uint32		junk_len;
+	uint8		info;
 
 	stats->count++;
 
 	rmid = XLogRecGetRmid(record);
+	info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
 
 	XLogDumpRecordLen(record, &rec_len, &fpi_len);
+	if(RM_XLOG_ID == rmid && XLOG_SWITCH == info)
+	{
+		junk_len = xlog_switch_junk_len(record);
+		stats->count_xlog_switch++;
+		stats->junk_size += junk_len;
+	}
 
 	/* Update per-rmgr statistics */
 
@@ -438,6 +450,14 @@ XLogDumpCountRecord(XLogDumpConfig *config, XLogDumpStats *stats,
 
 	recid = XLogRecGetInfo(record) >> 4;
 
+	/*
+	 * XXX: There is a special case for XACT records. Those records use the MSB
+	 * of recid for another purpose. Ignore that bit in that case.
+	 */
+	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;
@@ -610,6 +630,7 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
 	uint64		total_len = 0;
 	double		rec_len_pct,
 				fpi_len_pct;
+	const char 	*switch_junk_id;
 
 	/*
 	 * Each row shows its percentages of the total, so make a first pass to
@@ -622,7 +643,9 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
 		total_rec_len += stats->rmgr_stats[ri].rec_len;
 		total_fpi_len += stats->rmgr_stats[ri].fpi_len;
 	}
+	total_rec_len += stats->junk_size;
 	total_len = total_rec_len + total_fpi_len;
+	total_count += stats->count_xlog_switch;
 
 	/*
 	 * 27 is strlen("Transaction/COMMIT_PREPARED"), 20 is strlen(2^64), 8 is
@@ -652,12 +675,20 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
 			XLogDumpStatsRow(desc->rm_name,
 							 count, total_count, rec_len, total_rec_len,
 							 fpi_len, total_fpi_len, tot_len, total_len);
+			if(RM_XLOG_ID == ri)
+			{
+				switch_junk_id = "XLOGSwitchJunk";
+				XLogDumpStatsRow(psprintf("%s", switch_junk_id),
+									stats->count_xlog_switch, total_count, stats->junk_size, total_rec_len,
+									0, total_fpi_len, stats->junk_size, total_len);
+			}
 		}
 		else
 		{
 			for (rj = 0; rj < MAX_XLINFO_TYPES; rj++)
 			{
 				const char *id;
+				uint8		info;
 
 				count = stats->record_stats[ri][rj].count;
 				rec_len = stats->record_stats[ri][rj].rec_len;
@@ -676,6 +707,12 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
 				XLogDumpStatsRow(psprintf("%s/%s", desc->rm_name, id),
 								 count, total_count, rec_len, total_rec_len,
 								 fpi_len, total_fpi_len, tot_len, total_len);
+				info = (rj << 4) & ~XLR_INFO_MASK;
+				switch_junk_id = "XLOG/SWITCH_JUNK";
+				if( XLOG_SWITCH == info && stats->count_xlog_switch > 0)
+					XLogDumpStatsRow(psprintf("%s", switch_junk_id),
+									stats->count_xlog_switch, total_count, stats->junk_size, total_rec_len,
+									0, total_fpi_len, stats->junk_size, total_len);
 			}
 		}
 	}
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 4146753d47..8cbc309108 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -315,6 +315,7 @@ extern XLogRecPtr RequestXLogSwitch(bool mark_unimportant);
 
 extern void GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli);
 
+extern uint32 xlog_switch_junk_len(XLogReaderState *record);
 /*
  * Exported for the functions in timeline.c and xlogarchive.c.  Only valid
  * in the startup process.