From: Tom Lane Date: Fri, 13 Feb 2009 17:12:10 +0000 (+0000) Subject: Fix UNLISTEN to fall out quickly if the current backend has never executed X-Git-Tag: REL8_3_7~19 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=099186df32adfb41fe1daca916363469d5c28584;p=postgresql 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. --- diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c index 06ba738fd4..38fc57393e 100644 --- a/src/backend/commands/async.c +++ b/src/backend/commands/async.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.138.2.1 2008/03/12 20:11:54 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.138.2.2 2009/02/13 17:12:10 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -283,6 +283,10 @@ 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); } } @@ -298,6 +302,10 @@ 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, ""); }