From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Wed, 11 Feb 2026 16:50:57 +0000 (+0200)
Subject: Fix pg_stat_get_backend_wait_event() for aux processes
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=78a5e3074b824b4bbcb75ea4dd565ce735f54293;p=thirdparty%2Fpostgresql.git

Fix pg_stat_get_backend_wait_event() for aux processes

The pg_stat_activity view shows information for aux processes, but the
pg_stat_get_backend_wait_event() and
pg_stat_get_backend_wait_event_type() functions did not. To fix, call
AuxiliaryPidGetProc(pid) if BackendPidGetProc(pid) returns NULL, like
we do in pg_stat_get_activity().

In version 17 and above, it's a little silly to use those functions
when we already have the ProcNumber at hand, but it was necessary
before v17 because the backend ID was different from ProcNumber. I
have other plans for wait_event_info on master, so it doesn't seem
worth applying a different fix on different versions now.

Reviewed-by: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://www.postgresql.org/message-id/c0320e04-6e85-4c49-80c5-27cfb3a58108@iki.fi
Backpatch-through: 14
---

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 73ca0bb0b7f..b1df96e7b0b 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -824,8 +824,14 @@ pg_stat_get_backend_wait_event_type(PG_FUNCTION_ARGS)
 		wait_event_type = "<backend information not available>";
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))
 		wait_event_type = "<insufficient privilege>";
-	else if ((proc = BackendPidGetProc(beentry->st_procpid)) != NULL)
-		wait_event_type = pgstat_get_wait_event_type(proc->wait_event_info);
+	else
+	{
+		proc = BackendPidGetProc(beentry->st_procpid);
+		if (!proc)
+			proc = AuxiliaryPidGetProc(beentry->st_procpid);
+		if (proc)
+			wait_event_type = pgstat_get_wait_event_type(proc->wait_event_info);
+	}
 
 	if (!wait_event_type)
 		PG_RETURN_NULL();
@@ -845,8 +851,14 @@ pg_stat_get_backend_wait_event(PG_FUNCTION_ARGS)
 		wait_event = "<backend information not available>";
 	else if (!HAS_PGSTAT_PERMISSIONS(beentry->st_userid))
 		wait_event = "<insufficient privilege>";
-	else if ((proc = BackendPidGetProc(beentry->st_procpid)) != NULL)
-		wait_event = pgstat_get_wait_event(proc->wait_event_info);
+	else
+	{
+		proc = BackendPidGetProc(beentry->st_procpid);
+		if (!proc)
+			proc = AuxiliaryPidGetProc(beentry->st_procpid);
+		if (proc)
+			wait_event = pgstat_get_wait_event(proc->wait_event_info);
+	}
 
 	if (!wait_event)
 		PG_RETURN_NULL();