Subject: [PATCH v3] Fix test_custom_stats modules to error out when not preloaded

From: Bertrand Drouvot <[email-masked]>
Date: Thu, 2 Jul 2026 04:34:49 +0000

Previously, test_custom_var_stats and test_custom_fixed_stats silently
skipped pgstat_register_kind() when not loaded via shared_preload_libraries.
This left the SQL functions callable without the kind registered, leading to NULL
dereferences in core pgstat functions.

Remove the early return and let pgstat_register_kind() error out naturally,
matching the pattern used by test_custom_rmgrs with RegisterCustomRmgr(). Now
CREATE EXTENSION fails with a clear error if the module is not preloaded.

Author: Bertrand Drouvot <[email-masked]>
Reviewed-by: Ewan Young <[email-masked]>
Discussion: https://postgr.es/m/akS/ldidWeqG1FWk%40bdtpg
---
 .../modules/test_custom_stats/test_custom_fixed_stats.c  | 9 ++++-----
 .../modules/test_custom_stats/test_custom_var_stats.c    | 9 ++++-----
 2 files changed, 8 insertions(+), 10 deletions(-)
 100.0% src/test/modules/test_custom_stats/

diff --git a/src/test/modules/test_custom_stats/test_custom_fixed_stats.c b/src/test/modules/test_custom_stats/test_custom_fixed_stats.c
index a066ce117a6..8b29ca3e27a 100644
--- a/src/test/modules/test_custom_stats/test_custom_fixed_stats.c
+++ b/src/test/modules/test_custom_stats/test_custom_fixed_stats.c
@@ -72,11 +72,10 @@ static const PgStat_KindInfo custom_stats = {
 void
 _PG_init(void)
 {
-	/* Must be loaded via shared_preload_libraries */
-	if (!process_shared_preload_libraries_in_progress)
-		return;
-
-	/* Register custom statistics kind */
+	/*
+	 * In order to register our custom statistics kind, we have to be loaded
+	 * via shared_preload_libraries. Otherwise, registration will fail.
+	 */
 	pgstat_register_kind(PGSTAT_KIND_TEST_CUSTOM_FIXED_STATS, &custom_stats);
 }
 
diff --git a/src/test/modules/test_custom_stats/test_custom_var_stats.c b/src/test/modules/test_custom_stats/test_custom_var_stats.c
index 863d6a52492..fa415c81301 100644
--- a/src/test/modules/test_custom_stats/test_custom_var_stats.c
+++ b/src/test/modules/test_custom_stats/test_custom_var_stats.c
@@ -129,11 +129,10 @@ static const PgStat_KindInfo custom_stats = {
 void
 _PG_init(void)
 {
-	/* Must be loaded via shared_preload_libraries */
-	if (!process_shared_preload_libraries_in_progress)
-		return;
-
-	/* Register custom statistics kind */
+	/*
+	 * In order to register our custom statistics kind, we have to be loaded
+	 * via shared_preload_libraries. Otherwise, registration will fail.
+	 */
 	pgstat_register_kind(PGSTAT_KIND_TEST_CUSTOM_VAR_STATS, &custom_stats);
 }
 
-- 
2.34.1

--i51FQWZELabmlh2Y--