Add information about WAL buffers being full to EXPLAIN (WAL)

michaelpq · michaelpq · commit 320545bfcfee · 2025-02-17T14:50:33.000+09:00
This is similar to ce5bcc4, relying on the addition of wal_buffers_full to WalUsage. This time, the information is added to the output generated by EXPLAIN (WAL). Author: Bertrand Drouvot Reviewed-by: Ilia Evdokimov Discussion: https://postgr.es/m/Z6SOha5YFFgvpwQY@ip-10-97-1-34.eu-west-3.compute.internal
diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml
@@ -242,8 +242,9 @@ ROLLBACK;
     <listitem>
      <para>
       Include information on WAL record generation. Specifically, include the
-      number of records, number of full page images (fpi) and the amount of WAL
-      generated in bytes. In text format, only non-zero values are printed.
+      number of records, number of full page images (fpi), the amount of WAL
+      generated in bytes and the number of times the WAL buffers became full.
+      In text format, only non-zero values are printed.
       This parameter may only be used when <literal>ANALYZE</literal> is also
       enabled.  It defaults to <literal>FALSE</literal>.
      </para>
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
@@ -4242,7 +4242,7 @@ show_wal_usage(ExplainState *es, const WalUsage *usage)
 	{
 		/* Show only positive counter values. */
 		if ((usage->wal_records > 0) || (usage->wal_fpi > 0) ||
-			(usage->wal_bytes > 0))
+			(usage->wal_bytes > 0) || (usage->wal_buffers_full > 0))
 		{
 			ExplainIndentText(es);
 			appendStringInfoString(es->str, "WAL:");
@@ -4256,6 +4256,9 @@ show_wal_usage(ExplainState *es, const WalUsage *usage)
 			if (usage->wal_bytes > 0)
 				appendStringInfo(es->str, " bytes=" UINT64_FORMAT,
 								 usage->wal_bytes);
+			if (usage->wal_buffers_full > 0)
+				appendStringInfo(es->str, " buffers full=%lld",
+								 (long long) usage->wal_buffers_full);
 			appendStringInfoChar(es->str, '\n');
 		}
 	}
@@ -4267,6 +4270,8 @@ show_wal_usage(ExplainState *es, const WalUsage *usage)
 							   usage->wal_fpi, es);
 		ExplainPropertyUInteger("WAL Bytes", NULL,
 								usage->wal_bytes, es);
+		ExplainPropertyInteger("WAL Buffers Full", NULL,
+							   usage->wal_buffers_full, es);
 	}
 }
 

Original file line number	Diff line number	Diff line change
`@@ -4242,7 +4242,7 @@ show_wal_usage(ExplainState es, const WalUsage usage)`
`4242`	`4242`	`{`
`4243`	`4243`	`/* Show only positive counter values. */`
`4244`	`4244`	`if ((usage->wal_records > 0) \|\| (usage->wal_fpi > 0) \|\|`
`4245`		`- (usage->wal_bytes > 0))`
	`4245`	`+ (usage->wal_bytes > 0) \|\| (usage->wal_buffers_full > 0))`
`4246`	`4246`	`{`
`4247`	`4247`	`ExplainIndentText(es);`
`4248`	`4248`	`appendStringInfoString(es->str, "WAL:");`
`@@ -4256,6 +4256,9 @@ show_wal_usage(ExplainState es, const WalUsage usage)`
`4256`	`4256`	`if (usage->wal_bytes > 0)`
`4257`	`4257`	`appendStringInfo(es->str, " bytes=" UINT64_FORMAT,`
`4258`	`4258`	`usage->wal_bytes);`
	`4259`	`+ if (usage->wal_buffers_full > 0)`
	`4260`	`+ appendStringInfo(es->str, " buffers full=%lld",`
	`4261`	`+ (long long) usage->wal_buffers_full);`
`4259`	`4262`	`appendStringInfoChar(es->str, '\n');`
`4260`	`4263`	`}`
`4261`	`4264`	`}`
`@@ -4267,6 +4270,8 @@ show_wal_usage(ExplainState es, const WalUsage usage)`
`4267`	`4270`	`usage->wal_fpi, es);`
`4268`	`4271`	`ExplainPropertyUInteger("WAL Bytes", NULL,`
`4269`	`4272`	`usage->wal_bytes, es);`
	`4273`	`+ ExplainPropertyInteger("WAL Buffers Full", NULL,`
	`4274`	`+ usage->wal_buffers_full, es);`
`4270`	`4275`	`}`
`4271`	`4276`	`}`
`4272`	`4277`