From d4175f7ffc623c8d4acc283e51d8865017fa14e3 Mon Sep 17 00:00:00 2001
From: Shihao <zhong950419@gmail.com>
Date: Sun, 27 Sep 2026 09:58:16 -0700
Subject: [PATCH v1] Add test for standby restart after VM truncation

With full_page_writes off, records that clear VM bits carry no image of
the VM page. The test clears VM bits by delete, same-page update and
cross-page update, truncates the tables, and restarts the standby from a
restartpoint taken before those changes.

Discussion: https://postgr.es/m/CAL4mQLAp562c1rCgg2Dqx6TBSdOk6vOvaLFjwFG9E6k4uwvJJw@mail.gmail.com
---
 src/test/recovery/meson.build                |  1 +
 src/test/recovery/t/058_vm_clear_truncate.pl | 81 ++++++++++++++++++++
 2 files changed, 82 insertions(+)
 create mode 100644 src/test/recovery/t/058_vm_clear_truncate.pl

diff --git a/src/test/recovery/meson.build b/src/test/recovery/meson.build
index ebb12dd8766..bb28f9cfb81 100644
--- a/src/test/recovery/meson.build
+++ b/src/test/recovery/meson.build
@@ -66,6 +66,7 @@ tests += {
       't/055_cascade_reconnect.pl',
       't/056_standby_snapshot_export.pl',
       't/057_snapshot_commit_race.pl',
+      't/058_vm_clear_truncate.pl',
     ],
   },
 }
diff --git a/src/test/recovery/t/058_vm_clear_truncate.pl b/src/test/recovery/t/058_vm_clear_truncate.pl
new file mode 100644
index 00000000000..ee1f805b8eb
--- /dev/null
+++ b/src/test/recovery/t/058_vm_clear_truncate.pl
@@ -0,0 +1,81 @@
+
+# Copyright (c) 2026, PostgreSQL Global Development Group
+
+# A standby must be able to restart when WAL it replays again clears
+# visibility map bits on a VM page that a later, already replayed,
+# truncation removed.  With full_page_writes off, the clearing records
+# carry no image of the VM page, so redo has to cope with the page not
+# existing.
+use strict;
+use warnings FATAL => 'all';
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+my $primary = PostgreSQL::Test::Cluster->new('primary');
+$primary->init(allows_streaming => 1);
+$primary->append_conf(
+	'postgresql.conf', qq{
+full_page_writes = off
+autovacuum = off
+});
+$primary->start;
+$primary->backup('bkp');
+
+my $standby = PostgreSQL::Test::Cluster->new('standby');
+$standby->init_from_backup($primary, 'bkp', has_streaming => 1);
+$standby->start;
+
+# Make every heap page all-visible, then make the standby create a
+# restartpoint, so that a restart replays the changes below again.
+$primary->safe_psql(
+	'postgres', q{
+CREATE TABLE vm_del (a int);
+CREATE TABLE vm_hot (a int) WITH (fillfactor = 50);
+CREATE TABLE vm_upd (a int);
+INSERT INTO vm_del SELECT generate_series(1, 1000);
+INSERT INTO vm_hot SELECT generate_series(1, 1000);
+INSERT INTO vm_upd SELECT generate_series(1, 1000);
+VACUUM (FREEZE) vm_del, vm_hot, vm_upd;
+CHECKPOINT;
+});
+$primary->wait_for_replay_catchup($standby);
+$standby->safe_psql('postgres', 'CHECKPOINT');
+
+my $start_lsn =
+  $primary->safe_psql('postgres', 'SELECT pg_current_wal_insert_lsn()');
+
+# Clear VM bits through delete, same-page update (old VM block) and
+# cross-page update (new VM block), then truncate all three tables to
+# zero blocks.
+$primary->safe_psql(
+	'postgres', q{
+DELETE FROM vm_del;
+UPDATE vm_hot SET a = -a WHERE a = 1;
+UPDATE vm_upd SET a = -a WHERE a = 1;
+DELETE FROM vm_hot;
+DELETE FROM vm_upd;
+VACUUM vm_del, vm_hot, vm_upd;
+});
+is( $primary->safe_psql(
+		'postgres',
+		"SELECT sum(pg_relation_size(c, 'vm')) FROM unnest('{vm_del,vm_hot,vm_upd}'::regclass[]) c"
+	),
+	'0',
+	'VMs truncated on primary');
+$primary->wait_for_replay_catchup($standby);
+
+$standby->stop;
+my $log_offset = -s $standby->logfile;
+my $ret = $standby->start(fail_ok => 1);
+
+my $log = slurp_file($standby->logfile, $log_offset);
+my ($redo_lsn) = $log =~ /redo starts at ([0-9A-F]+\/[0-9A-F]+)/;
+ok( defined($redo_lsn)
+	  && $primary->safe_psql('postgres',
+		"SELECT '$redo_lsn'::pg_lsn < '$start_lsn'::pg_lsn") eq 't',
+	'redo after restart starts before the VM bits were cleared');
+ok($ret, 'standby restarts after replaying VM truncation');
+unlike($log, qr/invalid pages/, 'no invalid page references in standby log');
+
+done_testing();
-- 
2.37.1 (Apple Git-137.1)