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From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Subject: [PATCH v2 4/4] Add SQL-path test for read_local_xlog_page_guts() timeline race
Date: Tue, 9 Jun 2026 09:56:05 +0000

Extend the injection-point test in 035_standby_logical_decoding.pl to
also cover the SQL-callable decoding path (pg_logical_slot_peek_changes)
which exercises read_local_xlog_page_guts().

The test uses the same promotion and injection point as the walsender
test: a background psql session is connected before promotion, then
issues pg_logical_slot_peek_changes while startup is paused at the
injection point.

Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Discussion: https://postgr.es/m/7daef094-abf3-4672-bc23-3df4763b16a3%40gmail.com
---
 .../recovery/t/035_standby_logical_decoding.pl  | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)
 100.0% src/test/recovery/t/

diff --git a/src/test/recovery/t/035_standby_logical_decoding.pl b/src/test/recovery/t/035_standby_logical_decoding.pl
index 9b45c819241..6ec338ebf32 100644
--- a/src/test/recovery/t/035_standby_logical_decoding.pl
+++ b/src/test/recovery/t/035_standby_logical_decoding.pl
@@ -1068,11 +1068,13 @@ is($cascading_stdout, $expected,
 # timeline in this window.
 ##################################################
 
-# Create a logical slot on the cascading standby for this test.
+# Create logical slots on the cascading standby for this test.
 $node_cascading_standby->create_logical_slot_on_standby($node_standby,
 	'race_slot', 'testdb');
+$node_cascading_standby->create_logical_slot_on_standby($node_standby,
+	'race_slot_sql', 'testdb');
 
-# Insert data so the slot has WAL to decode.
+# Insert data so the slots have WAL to decode.
 $node_standby->safe_psql('testdb',
 	qq[INSERT INTO decoding_test(x,y) SELECT s, s::text FROM generate_series(10,13) s;]
 );
@@ -1089,6 +1091,9 @@ COMMIT};
 $node_standby->safe_psql('testdb', 'CREATE EXTENSION injection_points;');
 $node_standby->wait_for_replay_catchup($node_cascading_standby);
 
+# Open a background psql session BEFORE promotion for the SQL decoding test.
+my $decode_session = $node_cascading_standby->background_psql('testdb');
+
 # Attach injection point to pause startup after WAL segment cleanup
 # but before RecoveryInProgress() flips to false.
 $node_cascading_standby->safe_psql('testdb',
@@ -1130,6 +1135,14 @@ is($stdout2, $expected,
 	'got expected output from pg_recvlogical during promotion timeline switch'
 );
 
+# Verify SQL decoding (read_local_xlog_page_guts path) on the pre-connected
+# session.
+my $sql_out = $decode_session->query_safe(
+	"SELECT data FROM pg_logical_slot_peek_changes('race_slot_sql', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1')"
+);
+is($sql_out, $expected,
+	'pg_logical_slot_peek_changes works during promotion timeline switch');
+
 # Resume promotion.
 $node_cascading_standby->safe_psql('testdb',
 	"SELECT injection_points_wakeup('promotion-after-wal-segment-cleanup');");
-- 
2.34.1


--Wctt8FE9hhxDGrBZ--

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  To: pgsql-hackers@postgresql.org
  Cc: bertranddrouvot.pg@gmail.com
  Subject: Re: [PATCH v2 4/4] Add SQL-path test for read_local_xlog_page_guts() timeline race
  In-Reply-To: <no-message-id-1733609@localhost>

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