From 85f1b4070bcabdac73a97c3b06a64cf27673eb20 Mon Sep 17 00:00:00 2001
From: Vitaly Davydov <v.davydov@postgrespro.ru>
Date: Sun, 26 Oct 2025 11:22:54 +0300
Subject: [PATCH] Test a specific case of physical slot invalidation

When ReplicationSlotReserveWal() succeeds to read old RedoRecPtr
right before the assignment of a new RedoRecPtr in a checkpointer
which runs in parallel, the created slot may be invalidated.
---
 src/backend/replication/slot.c                |   4 +
 ..._create_physlcal_slot_during_checkpoint.pl | 121 ++++++++++++++++++
 2 files changed, 125 insertions(+)
 create mode 100644 src/test/recovery/t/100_create_physlcal_slot_during_checkpoint.pl

diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index ac188bb2f77..4310589da26 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1578,10 +1578,14 @@ ReplicationSlotReserveWal(void)
 		else
 			restart_lsn = GetXLogInsertRecPtr();
 
+		INJECTION_POINT("physical-slot-reserve-wal-get-redo", NULL);
+
 		SpinLockAcquire(&slot->mutex);
 		slot->data.restart_lsn = restart_lsn;
 		SpinLockRelease(&slot->mutex);
 
+		INJECTION_POINT("physical-slot-reserve-wal-before-compute-required-lsn", NULL);
+
 		/* prevent WAL removal as fast as possible */
 		ReplicationSlotsComputeRequiredLSN();
 
diff --git a/src/test/recovery/t/100_create_physlcal_slot_during_checkpoint.pl b/src/test/recovery/t/100_create_physlcal_slot_during_checkpoint.pl
new file mode 100644
index 00000000000..f3211e210a5
--- /dev/null
+++ b/src/test/recovery/t/100_create_physlcal_slot_during_checkpoint.pl
@@ -0,0 +1,121 @@
+# This test checks that the new slot maybe invalidated by checkpoint
+
+use strict;
+use warnings;
+use Config;
+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';
+}
+
+my $res;
+
+# Setup primary node
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init(allows_streaming => 1);
+
+$node->append_conf('postgresql.conf', q{
+	wal_level = logical
+	checkpoint_timeout = 30min
+	checkpoint_completion_target = 0.1
+});
+
+$node->start();
+$node->safe_psql('postgres', q{create extension injection_points;});
+
+my $createslot = $node->background_psql('postgres');
+my $checkpoint = $node->background_psql('postgres');
+
+sub physreplslot_start_create()
+{
+	$createslot->query_until(
+		qr/start-create-slot/,
+		q(\echo start-create-slot
+		select pg_create_physical_replication_slot('standby1', true);
+	));
+}
+
+sub checkpoint_start()
+{
+	$checkpoint->query_until(
+		qr/start-checkpoint/,
+		q(\echo start-checkpoint
+		checkpoint;
+	));
+}
+
+sub injection_point_attach($$)
+{
+	my ($injectpname, $event) = @_;
+
+	$node->safe_psql('postgres', "select injection_points_attach('$injectpname','$event')");
+}
+
+sub injection_point_detach($)
+{
+	my $injectpname = shift;
+
+	$node->safe_psql('postgres', "select injection_points_detach('$injectpname');");
+}
+
+sub injection_point_wait($$)
+{
+	my ($subsystem, $injectpname) = @_;
+
+	note("waiting for $injectpname injection point");
+	$node->wait_for_event($subsystem, $injectpname);
+	note("injection_point $injectpname is reached");
+}
+
+sub injection_point_wakeup($)
+{
+	my $injectpname = shift;
+
+	$node->safe_psql('postgres', "select injection_points_wakeup('$injectpname');");
+}
+
+sub get_slot_invalidation_state($)
+{
+	my $slotname = shift;
+
+	return $node->safe_psql('postgres',
+		"select invalidation_reason from pg_replication_slots where slot_name='$slotname'");
+}
+
+injection_point_attach('physical-slot-reserve-wal-get-redo', 'wait');
+injection_point_attach('checkpoint-before-old-wal-removal', 'wait');
+injection_point_attach("physical-slot-reserve-wal-before-compute-required-lsn", 'wait');
+
+# start create physical replication slot
+physreplslot_start_create();
+
+# reach the get-redo injection point and stop there
+injection_point_wait('client backend', 'physical-slot-reserve-wal-get-redo');
+
+$node->advance_wal(6);
+
+# start checkpoint
+checkpoint_start();
+
+# reach the injection point before old WAL removal and stop there
+injection_point_wait('checkpointer', 'checkpoint-before-old-wal-removal');
+
+injection_point_wakeup('physical-slot-reserve-wal-get-redo');
+
+injection_point_wakeup('checkpoint-before-old-wal-removal');
+
+injection_point_wakeup('physical-slot-reserve-wal-before-compute-required-lsn');
+
+# complete physical slot creation
+eval { $createslot->quit(); };
+
+# complete checkpoint
+eval { $checkpoint->quit(); };
+
+is(get_slot_invalidation_state('standby1'), "", "slot is not invalidated by checkpoint");
+
+done_testing();
-- 
2.43.0