From a7b9bca6236a68f77ed2ee18eb08a9081345e768 Mon Sep 17 00:00:00 2001
From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Date: Mon, 2 Nov 2026 14:55:40 +0000
Subject: [PATCH v1 2/2] Test heap rescan strategy changes

---
 src/test/modules/test_misc/meson.build        |  1 +
 .../test_misc/t/016_heap_rescan_strategy.pl   | 81 +++++++++++++++++++
 2 files changed, 82 insertions(+)
  97.9% src/test/modules/test_misc/t/

diff --git a/src/test/modules/test_misc/meson.build b/src/test/modules/test_misc/meson.build
index 5d81f5b13be..b5e98fd0233 100644
--- a/src/test/modules/test_misc/meson.build
+++ b/src/test/modules/test_misc/meson.build
@@ -24,6 +24,7 @@ tests += {
       't/013_temp_obj_multisession.pl',
       't/014_log_statement_max_length.pl',
       't/015_temp_schema_exit_deferrable.pl',
+      't/016_heap_rescan_strategy.pl',
     ],
     # The injection points are cluster-wide, so disable installcheck
     'runningcheck': false,
diff --git a/src/test/modules/test_misc/t/016_heap_rescan_strategy.pl b/src/test/modules/test_misc/t/016_heap_rescan_strategy.pl
new file mode 100644
index 00000000000..01007a3c737
--- /dev/null
+++ b/src/test/modules/test_misc/t/016_heap_rescan_strategy.pl
@@ -0,0 +1,81 @@
+# Copyright (c) 2026, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+# Set a low threshold for selecting a bulk-read strategy.
+my $node = PostgreSQL::Test::Cluster->new('main');
+$node->init;
+$node->append_conf(
+	'postgresql.conf', qq{
+shared_buffers = '1MB'
+max_parallel_workers_per_gather = 0
+});
+$node->start;
+
+$node->safe_psql(
+	'postgres', q{
+CREATE TABLE growing AS
+  SELECT g, repeat('x', 1000) AS payload
+  FROM generate_series(1, 16) AS g;
+CREATE TABLE growth_done (done boolean PRIMARY KEY);
+
+CREATE FUNCTION grow_table(should_grow boolean)
+RETURNS integer
+LANGUAGE plpgsql
+VOLATILE
+AS $$
+DECLARE
+  inserted boolean;
+BEGIN
+  IF should_grow THEN
+    INSERT INTO growth_done VALUES (true)
+      ON CONFLICT DO NOTHING
+      RETURNING true INTO inserted;
+
+    IF inserted THEN
+      INSERT INTO growing
+        SELECT g, repeat('y', 1000)
+        FROM generate_series(17, 4000) AS g;
+    END IF;
+  END IF;
+
+  RETURN 1;
+END
+$$;
+});
+
+# Grow the relation during the second scan.  The third rescan must recreate
+# its read stream with the newly selected bulk-read strategy.
+my $bulkread = $node->safe_psql(
+	'postgres', q{
+SET enable_material = off;
+SET enable_memoize = off;
+SELECT count(*) AS scan_count
+FROM (VALUES (1, false), (2, true), (3, false)) AS v(ord, should_grow)
+CROSS JOIN LATERAL (
+  SELECT *
+  FROM growing
+  WHERE g >= grow_table(v.should_grow)
+  OFFSET 0
+) AS s
+\gset
+
+SELECT pg_stat_force_next_flush()
+\gset
+
+SELECT COALESCE(sum(reads), 0) + COALESCE(sum(hits), 0)
+FROM pg_stat_get_backend_io(pg_backend_pid())
+WHERE object = 'relation'
+  AND context = 'bulkread';
+});
+
+cmp_ok($bulkread, '>', 0,
+	'a rescanned sequential scan uses its newly selected bulk-read strategy');
+
+$node->stop;
+done_testing();
-- 
2.34.1