From 20f33d76aa412e3f5c0c6ec422b7c27eb0ae6f89 Mon Sep 17 00:00:00 2001
From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Date: Thu, 6 Feb 2025 08:26:26 +0000
Subject: [PATCH v1 3/3] Allow EXPLAIN to track WAL buffers full

Now that wal_buffers_full is part of the WalUsage struct, let's report it in
explain/auto_explain when the WAL option/auto_explain.log_wal is enabled.
---
 doc/src/sgml/ref/explain.sgml  | 5 +++--
 src/backend/commands/explain.c | 5 +++++
 2 files changed, 8 insertions(+), 2 deletions(-)
  61.8% doc/src/sgml/ref/
  38.1% src/backend/commands/

diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml
index 6361a14e65d..652ece7213a 100644
--- 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
index c24e66f82e1..0512eb49733 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -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);
 	}
 }
 
-- 
2.34.1

