Fix the check to limit sync workers.

Amit Kapila · Amit Kapila · commit 59348fbdeb7b · 2022-04-19T09:18:44.000+05:30
We don't allow to invoke more sync workers once we have reached the sync worker limit per subscription. But the check to enforce this also doesn't allow to launch an apply worker if it gets restarted. This code was introduced by commit de43897 but we caught the problem only with the test added by recent commit c91f71b which started failing occasionally in the buildfarm. As per buildfarm. Diagnosed-by: Amit Kapila, Masahiko Sawada, Tomas Vondra Author: Amit Kapila Backpatch-through: 10 Discussion: https://postgr.es/m/CAH2L28vddB_NFdRVpuyRBJEBWjz4BSyTB=_ektNRH8NJ1jf95g@mail.gmail.com https://postgr.es/m/f90d2b03-4462-ce95-a524-d91464e797c8@enterprisedb.com
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
@@ -372,11 +372,11 @@ logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname, Oid userid,
 	}
 
 	/*
-	 * If we reached the sync worker limit per subscription, just exit
-	 * silently as we might get here because of an otherwise harmless race
-	 * condition.
+	 * We don't allow to invoke more sync workers once we have reached the sync
+	 * worker limit per subscription. So, just return silently as we might get
+	 * here because of an otherwise harmless race condition.
 	 */
-	if (nsyncworkers >= max_sync_workers_per_subscription)
+	if (OidIsValid(relid) && nsyncworkers >= max_sync_workers_per_subscription)
 	{
 		LWLockRelease(LogicalRepWorkerLock);
 		return;
