From a468549cc9414f6a132ff9927ed3704ce2354698 Mon Sep 17 00:00:00 2001
From: alterego655 <824662526@qq.com>
Date: Thu, 22 Oct 2026 17:36:14 +0800
Subject: [PATCH v1 2/2] Test pg_walinspect reads across historical timelines

Read a record that crosses into the first segment of a historical
timeline with pg_get_wal_record_info().  XLogFindNextRecord() rewinds
to the record's start after reading it, which used to select a
timeline with no file for that segment.

Enable TAP tests for pg_walinspect.
---
 contrib/pg_walinspect/Makefile          |  1 +
 contrib/pg_walinspect/meson.build       |  5 +++
 contrib/pg_walinspect/t/001_timeline.pl | 52 +++++++++++++++++++++++++
 3 files changed, 58 insertions(+)
 create mode 100644 contrib/pg_walinspect/t/001_timeline.pl

diff --git a/contrib/pg_walinspect/Makefile b/contrib/pg_walinspect/Makefile
index 22090f7716c..77efe3afd7f 100644
--- a/contrib/pg_walinspect/Makefile
+++ b/contrib/pg_walinspect/Makefile
@@ -10,6 +10,7 @@ EXTENSION = pg_walinspect
 DATA = pg_walinspect--1.0.sql pg_walinspect--1.0--1.1.sql
 
 REGRESS = pg_walinspect oldextversions
+TAP_TESTS = 1
 
 REGRESS_OPTS = --temp-config $(top_srcdir)/contrib/pg_walinspect/walinspect.conf
 
diff --git a/contrib/pg_walinspect/meson.build b/contrib/pg_walinspect/meson.build
index 82ab186c340..e155a453aa1 100644
--- a/contrib/pg_walinspect/meson.build
+++ b/contrib/pg_walinspect/meson.build
@@ -27,6 +27,11 @@ tests += {
   'name': 'pg_walinspect',
   'sd': meson.current_source_dir(),
   'bd': meson.current_build_dir(),
+  'tap': {
+    'tests': [
+      't/001_timeline.pl',
+    ],
+  },
   'regress': {
     'sql': [
       'pg_walinspect',
diff --git a/contrib/pg_walinspect/t/001_timeline.pl b/contrib/pg_walinspect/t/001_timeline.pl
new file mode 100644
index 00000000000..6bdef43c6de
--- /dev/null
+++ b/contrib/pg_walinspect/t/001_timeline.pl
@@ -0,0 +1,52 @@
+# Copyright (c) 2026, PostgreSQL Global Development Group
+
+# Test timeline selection when XLogFindNextRecord() reads a record spanning
+# segments and then rewinds to its beginning.
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+my $node = PostgreSQL::Test::Cluster->new('main');
+$node->init(allows_streaming => 1, extra => ['--wal-segsize=1']);
+# Keep old segments across the checkpoints that follow each promotion.
+$node->append_conf('postgresql.conf', "wal_keep_size = '64MB'");
+$node->start;
+$node->safe_psql('postgres', 'CREATE EXTENSION pg_walinspect');
+
+# Write a record larger than a segment, starting right after a segment
+# switch.  It begins in segment N and ends about halfway through N+1.
+$node->safe_psql('postgres', 'SELECT pg_switch_wal()');
+my $before = $node->lsn('insert');
+my $record_end = $node->safe_psql('postgres',
+	"SELECT pg_logical_emit_message(false, 'test', repeat('x', 1536 * 1024), true)"
+);
+my $record_start = $node->safe_psql(
+	'postgres', qq[
+	SELECT start_lsn FROM pg_get_wal_records_info('$before', '$record_end')
+	WHERE resource_manager = 'LogicalMessage';
+]);
+
+# Restart in standby mode and promote, switching to a new timeline.
+# Timeline 2 begins in segment N+1, so it has no copy of segment N.
+$node->set_standby_mode;
+$node->restart;
+$node->promote;
+
+# Timeline 3 begins in a later segment, so segment N+1 stays on timeline 2.
+$node->safe_psql('postgres', 'SELECT pg_switch_wal()');
+$node->set_standby_mode;
+$node->restart;
+$node->promote;
+
+# Reading the record leaves the reader on timeline 2's copy of segment N+1.
+# Rewinding to the record's start must return to timeline 1's segment N.
+my ($ret, $stdout, $stderr) = $node->psql('postgres',
+	"SELECT end_lsn FROM pg_get_wal_record_info('$record_start')");
+is($stdout, $record_end,
+	'reread a cross-segment record after its timeline became historical')
+  or diag($stderr);
+
+done_testing();
-- 
2.51.0