From ac838953de9c4ab0cb5f13d1e1b8ad0a18e73e39 Mon Sep 17 00:00:00 2001
From: reshke <reshke@double.cloud>
Date: Thu, 18 Dec 2025 18:00:22 +0000
Subject: [PATCH v1] Add TAP test for empty page vacuum.

VACUUM can be run for empty pages with DISABLE_PAGE_SKIPPING option.
In this case, VACUUM wil set up page-level visibility bit
(PD_ALL_VISIBLE) if not previously set.
To end up with empty page which is missing visibility hint bit, we need
to forcefuly cancel (kill -9) backend, executing page freezing, jsut
after it did page pruning. Use injeciton point for this purpose and
add TAP test to cover "recovery" after error code path.
---
 src/backend/access/heap/vacuumlazy.c          |  6 ++
 .../test_misc/t/010_vacuum_empty_page.pl      | 75 +++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 src/test/modules/test_misc/t/010_vacuum_empty_page.pl

diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index 30778a15639..9b8cbb67f11 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -153,6 +153,7 @@
 #include "storage/freespace.h"
 #include "storage/lmgr.h"
 #include "storage/read_stream.h"
+#include "utils/injection_point.h"
 #include "utils/lsyscache.h"
 #include "utils/pg_rusage.h"
 #include "utils/timestamp.h"
@@ -1899,6 +1900,8 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno,
 		 */
 		if (!PageIsAllVisible(page))
 		{
+			INJECTION_POINT("vacuum-empty-page-non-all-vis", NULL);
+
 			START_CRIT_SECTION();
 
 			/* mark buffer dirty before writing a WAL record */
@@ -2012,6 +2015,9 @@ lazy_scan_prune(LVRelState *vacrel,
 							   &vacrel->offnum,
 							   &vacrel->NewRelfrozenXid, &vacrel->NewRelminMxid);
 
+	
+	INJECTION_POINT("vacuum-heap-prune-and-freeze-after", NULL);
+
 	Assert(MultiXactIdIsValid(vacrel->NewRelminMxid));
 	Assert(TransactionIdIsValid(vacrel->NewRelfrozenXid));
 
diff --git a/src/test/modules/test_misc/t/010_vacuum_empty_page.pl b/src/test/modules/test_misc/t/010_vacuum_empty_page.pl
new file mode 100644
index 00000000000..af5c39d2435
--- /dev/null
+++ b/src/test/modules/test_misc/t/010_vacuum_empty_page.pl
@@ -0,0 +1,75 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Check how temporary file removals and statement queries are associated
+# in the server logs for various query sequences with the simple and
+# extended query protocols.
+
+use strict;
+use warnings FATAL => 'all';
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+if ($ENV{enable_injection_points} ne 'yes')
+{
+	plan skip_all => 'Injection points not supported by this build';
+}
+
+# Initialize a new PostgreSQL test cluster
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init();
+$node->append_conf(
+	'postgresql.conf', qq(
+log_min_messages = 'notice'
+));
+$node->start;
+
+# Check if the extension injection_points is available, as it may be
+# possible that this script is run with installcheck, where the module
+# would not be installed by default.
+if (!$node->check_extension('injection_points'))
+{
+	plan skip_all => 'Extension injection_points not installed';
+}
+
+$node->safe_psql('postgres', 'CREATE EXTENSION injection_points;');
+
+
+# Setup table and populate with data
+$node->safe_psql(
+	"postgres", qq{
+CREATE TABLE vac_empty_test(a int);
+BEGIN;
+INSERT INTO vac_empty_test DEFAULT VALUES;
+ROLLBACK;
+});
+
+# From this point, autovacuum worker will wait at startup.
+$node->safe_psql('postgres',
+	"SELECT injection_points_attach('vacuum-heap-prune-and-freeze-after', 'error');");
+$node->safe_psql('postgres',
+	"SELECT injection_points_attach('vacuum-empty-page-non-all-vis', 'notice');");
+
+$node->psql('postgres', "VACUUM (FREEZE) vac_empty_test;", on_error_stop => 1);
+
+my $offset = -s $node->logfile;
+
+# Run vacuum, force it on empty page. 
+$node->safe_psql(
+	"postgres", qq{
+VACUUM (DISABLE_PAGE_SKIPPING) vac_empty_test;
+});
+
+ok( $node->log_contains(
+		qr/NOTICE:  notice triggered for injection point vacuum-empty-page-non-all-vis/,
+		$offset),
+	"vacuum sets all-visible page bit for empty page");
+
+
+$node->safe_psql('postgres',
+	"SELECT injection_points_detach('vacuum-heap-prune-and-freeze-after');");
+$node->safe_psql('postgres',
+	"SELECT injection_points_detach('vacuum-empty-page-non-all-vis');");
+
+$node->stop('fast');
+done_testing();
-- 
2.43.0