Subject: [PATCH v10 6/6] Expose WAL usage counters in verbose (auto)vacuum output.

From: Julien Rouhaud <[email-masked]>
Date: Thu, 19 Mar 2020 16:08:47 +0100

Author: Julien Rouhaud
Reviewed-by: Fuji Masao
Discussion: https://postgr.es/m/CAB-hujrP8ZfUkvL5OYETipQwA=e3n7oqHFU=[email-masked]
---
 src/backend/access/heap/vacuumlazy.c | 24 +++++++++++++++++++++++-
 src/backend/commands/explain.c       |  2 +-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index cc7e8521a5..735087dd74 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -410,6 +410,8 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 	int			nindexes;
 	PGRUsage	ru0;
 	TimestampTz starttime = 0;
+	WalUsage walusage_start = pgWalUsage;
+	WalUsage walusage = {0, 0, 0};
 	long		secs;
 	int			usecs;
 	double		read_rate,
@@ -614,6 +616,9 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 
 			TimestampDifference(starttime, endtime, &secs, &usecs);
 
+			memset(&walusage, 0, sizeof(WalUsage));
+			WalUsageAccumDiff(&walusage, &pgWalUsage, &walusage_start);
+
 			read_rate = 0;
 			write_rate = 0;
 			if ((secs > 0) || (usecs > 0))
@@ -666,7 +671,13 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 							 (long long) VacuumPageDirty);
 			appendStringInfo(&buf, _("avg read rate: %.3f MB/s, avg write rate: %.3f MB/s\n"),
 							 read_rate, write_rate);
-			appendStringInfo(&buf, _("system usage: %s"), pg_rusage_show(&ru0));
+			appendStringInfo(&buf, _("system usage: %s\n"), pg_rusage_show(&ru0));
+			appendStringInfo(&buf,
+							 _("WAL usage: %ld records, %ld full page writes, "
+							 UINT64_FORMAT " bytes"),
+							 walusage.wal_records,
+							 walusage.wal_num_fpw,
+							 walusage.wal_bytes);
 
 			ereport(LOG,
 					(errmsg_internal("%s", buf.data)));
@@ -758,6 +769,8 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 	IndexBulkDeleteResult **indstats;
 	int			i;
 	PGRUsage	ru0;
+	WalUsage walusage_start = pgWalUsage;
+	WalUsage walusage = {0, 0, 0};
 	Buffer		vmbuffer = InvalidBuffer;
 	BlockNumber next_unskippable_block;
 	bool		skipping_blocks;
@@ -1727,6 +1740,15 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 									"%u pages are entirely empty.\n",
 									empty_pages),
 					 empty_pages);
+
+	memset(&walusage, 0, sizeof(WalUsage));
+	WalUsageAccumDiff(&walusage, &pgWalUsage, &walusage_start);
+	appendStringInfo(&buf, _("%ld WAL records, %ld WAL full page writes, "
+							UINT64_FORMAT " WAL bytes\n"),
+							walusage.wal_records,
+							walusage.wal_num_fpw,
+							walusage.wal_bytes);
+
 	appendStringInfo(&buf, _("%s."), pg_rusage_show(&ru0));
 
 	ereport(elevel,
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index b05b55979b..f7f1c3efce 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -3105,7 +3105,7 @@ show_wal_usage(ExplainState *es, const WalUsage *usage)
 	{
 		ExplainPropertyInteger("WAL records", NULL,
 							   usage->wal_records, es);
-		ExplainPropertyInteger("WAL full page records", NULL,
+		ExplainPropertyInteger("WAL full page writes", NULL,
 							   usage->wal_num_fpw, es);
 		ExplainPropertyUInteger("WAL bytes", NULL,
 							   usage->wal_bytes, es);
-- 
2.20.1

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