Author:     Noah Misch <noah@leadboat.com>
Commit:     Noah Misch <noah@leadboat.com>

    

diff --git a/contrib/amcheck/t/089_vac.pl b/contrib/amcheck/t/089_vac.pl
new file mode 100644
index 0000000..a28ebd9
--- /dev/null
+++ b/contrib/amcheck/t/089_vac.pl
@@ -0,0 +1,50 @@
+
+# Copyright (c) 2021-2024, PostgreSQL Global Development Group
+
+# Test VACUUM vs. slow autovac
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+
+use Test::More;
+
+my ($node, $result);
+
+#
+# Test set-up
+#
+$node = PostgreSQL::Test::Cluster->new('main');
+$node->init;
+$node->append_conf('postgresql.conf', 'autovacuum_naptime = 1s');
+$node->append_conf('postgresql.conf', 'log_lock_waits = on');
+$node->append_conf('postgresql.conf', 'deadlock_timeout = 10ms');
+$node->append_conf('postgresql.conf', q{backtrace_functions = 'ProcessInterrupts'});
+$node->start;
+
+my $grant_h = $node->background_psql('postgres');
+
+# This running would block all vac_update_datfrozenxid => lock_timeout always
+# $grant_h->query_safe(
+# 	q(
+# BEGIN;
+# GRANT TEMP ON DATABASE postgres TO pg_monitor;
+# ));
+
+{
+	local $ENV{PGOPTIONS} = '-clock_timeout=5s';
+$node->pgbench(
+	'--no-vacuum --client=1 --time=600',
+	0,
+	[qr{actually processed}],
+	[qr{^$}],
+	'vac',
+	{
+		'vac' => 'VACUUM (ONLY_DATABASE_STATS);',
+	});
+}
+
+$grant_h->quit;
+$node->stop;
+done_testing();
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index ac8f5d9..20fe426 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -1582,6 +1582,7 @@ vac_update_relstats(Relation relation,
  *		commits.  As with vac_update_relstats, this avoids leaving dead tuples
  *		behind after a VACUUM.
  */
+#include "utils/fmgrprotos.h"
 void
 vac_update_datfrozenxid(void)
 {
@@ -1607,6 +1608,9 @@ vac_update_datfrozenxid(void)
 	 */
 	LockDatabaseFrozenIds(ExclusiveLock);
 
+	if (AmAutoVacuumWorkerProcess())
+		DirectFunctionCall1(pg_sleep, Float8GetDatum(10.0));
+
 	/*
 	 * Initialize the "min" calculation with
 	 * GetOldestNonRemovableTransactionId(), which is a reasonable