From 07dd5ecd204420678a100b64a01347227f4fef4f Mon Sep 17 00:00:00 2001
From: Jim Jones <jim.jones@uni-muenster.de>
Date: Wed, 8 Apr 2026 14:56:57 +0200
Subject: [PATCH v16 2/2] Test cross-session access on temporary tables

---
 src/test/modules/test_misc/meson.build        |   1 +
 .../test_misc/t/012_temp_obj_multisession.pl  | 117 ++++++++++++++++++
 2 files changed, 118 insertions(+)
 create mode 100644 src/test/modules/test_misc/t/012_temp_obj_multisession.pl

diff --git a/src/test/modules/test_misc/meson.build b/src/test/modules/test_misc/meson.build
index 1b25d98f7f3..a54599cc301 100644
--- a/src/test/modules/test_misc/meson.build
+++ b/src/test/modules/test_misc/meson.build
@@ -20,6 +20,7 @@ tests += {
       't/009_log_temp_files.pl',
       't/010_index_concurrently_upsert.pl',
       't/011_lock_stats.pl',
+      't/012_temp_obj_multisession.pl',
     ],
     # The injection points are cluster-wide, so disable installcheck
     'runningcheck': false,
diff --git a/src/test/modules/test_misc/t/012_temp_obj_multisession.pl b/src/test/modules/test_misc/t/012_temp_obj_multisession.pl
new file mode 100644
index 00000000000..4d599152740
--- /dev/null
+++ b/src/test/modules/test_misc/t/012_temp_obj_multisession.pl
@@ -0,0 +1,117 @@
+# Copyright (c) 2026, PostgreSQL Global Development Group
+
+use strict;
+use warnings;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::BackgroundPsql;
+use Test::More;
+
+# Set up a fresh node
+my $node = PostgreSQL::Test::Cluster->new('temp_lock');
+$node->init;
+$node->start;
+
+# Create a long-lived session
+my $psql1 = $node->background_psql('postgres');
+
+$psql1->query_safe(
+	q(CREATE TEMP TABLE foo AS SELECT 42 AS val;));
+
+# Create an index so the index-scan path (ReadBufferExtended) can be tested
+$psql1->query_safe(
+	q(CREATE INDEX ON foo(val);));
+
+my $tempschema = $node->safe_psql(
+    'postgres',
+    q{
+      SELECT n.nspname
+      FROM pg_class c
+      JOIN pg_namespace n ON n.oid = c.relnamespace
+      WHERE relname = 'foo' AND relpersistence = 't';
+    }
+);
+chomp $tempschema;
+ok($tempschema =~ /^pg_temp_\d+$/, "got temp schema: $tempschema");
+
+
+# SELECT TEMPORARY TABLE from other session
+my ($stdout, $stderr);
+$node->psql(
+    'postgres',
+    "SELECT val FROM $tempschema.foo;",
+    stdout => \$stdout,
+    stderr => \$stderr
+);
+like($stderr, qr/cannot access temporary relations of other sessions/,
+     'SELECT on other session temp table is not allowed');
+
+# UPDATE TEMPORARY TABLE from other session
+$node->psql(
+    'postgres',
+    "UPDATE $tempschema.foo SET val = NULL;",
+    stderr => \$stderr
+);
+like($stderr, qr/cannot access temporary relations of other sessions/,
+     'UPDATE on other session temp table is not allowed');
+
+# DELETE records from TEMPORARY TABLE from other session
+$node->psql(
+    'postgres',
+    "DELETE FROM $tempschema.foo;",
+    stderr => \$stderr
+);
+like($stderr, qr/cannot access temporary relations of other sessions/,
+     'DELETE on other session temp table is not allowed');
+
+# TRUNCATE TEMPORARY TABLE from other session
+$node->psql(
+    'postgres',
+    "TRUNCATE TABLE $tempschema.foo;",
+    stderr => \$stderr
+);
+like($stderr, qr/cannot truncate temporary tables of other sessions/,
+     'TRUNCATE on other session temp table is not allowed');
+
+# INSERT INTO TEMPORARY TABLE from other session
+$node->psql(
+    'postgres',
+    "INSERT INTO $tempschema.foo VALUES (73);",
+    stderr => \$stderr
+);
+like($stderr, qr/cannot access temporary relations of other sessions/,
+     'INSERT INTO on other session temp table is not allowed');
+
+# COPY TEMPORARY TABLE from other session
+$node->psql(
+    'postgres',
+    "COPY $tempschema.foo TO STDOUT;",
+    stderr => \$stderr
+);
+like($stderr, qr/cannot access temporary relations of other sessions/,
+     'COPY on other session temp table is blocked');
+
+# SELECT via index scan from other session.
+# Sequential scans are blocked at read_stream_begin_relation(); index scans
+# bypass that path entirely and reach ReadBufferExtended() in bufmgr.c
+# (nbtree's _bt_getbuf calls ReadBuffer directly for individual page fetches).
+# enable_seqscan=off forces the planner to use the index.
+$node->psql(
+    'postgres',
+    "SET enable_seqscan = off; SELECT val FROM $tempschema.foo WHERE val = 42;",
+    stderr => \$stderr
+);
+like($stderr, qr/cannot access temporary relations of other sessions/,
+     'index scan on other session temp table is not allowed (exercises ReadBufferExtended path)');
+
+# DROP TEMPORARY TABLE from other session
+my $ok = $node->psql(
+    'postgres',
+    "DROP TABLE $tempschema.foo;"
+);
+ok($ok == 0, 'DROP TABLE executed successfully');
+
+# Clean up
+$psql1->quit;
+
+done_testing();
-- 
2.43.0