From 5d2a33cc53db4d1996c81ab09c879ab8e5f31acb Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 13 Feb 2009 17:12:04 +0000 Subject: [PATCH] Fix UNLISTEN to fall out quickly if the current backend has never executed any LISTEN command. This is more important than it used to be because DISCARD ALL invokes UNLISTEN. Connection-pooled applications making heavy use of DISCARD ALL were seeing significant contention for pg_listener, as reported by Matteo Beccati. It seems unlikely that clients using LISTEN would use pooled connections, so this simple tweak seems sufficient, especially since the pg_listener implementation is slated to go away soon anyway. Back-patch to 8.3, where DISCARD ALL was introduced. --- src/backend/commands/async.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c index a6b93e5910..d410b2d47d 100644 --- a/src/backend/commands/async.c +++ b/src/backend/commands/async.c @@ -277,6 +277,10 @@ Async_Unlisten(const char *relname) if (Trace_notify) elog(DEBUG1, "Async_Unlisten(%s,%d)", relname, MyProcPid); + /* If we couldn't possibly be listening, no need to queue anything */ + if (pendingActions == NIL && !unlistenExitRegistered) + return; + queue_listen(LISTEN_UNLISTEN, relname); } @@ -291,6 +295,10 @@ Async_UnlistenAll(void) if (Trace_notify) elog(DEBUG1, "Async_UnlistenAll(%d)", MyProcPid); + /* If we couldn't possibly be listening, no need to queue anything */ + if (pendingActions == NIL && !unlistenExitRegistered) + return; + queue_listen(LISTEN_UNLISTEN_ALL, ""); } -- 2.39.5