notify-optimisation.diff

diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index 588e9f2..16c0d96 100644
--- a/src/backend/commands/async.c
+++ b/src/backend/commands/async.c
@@ -2160,7 +2160,6 @@ NotifyMyFrontEnd(const char *channel, const char *payload, int32 srcPid)
 static bool
 AsyncExistsPendingNotify(const char *channel, const char *payload)
 {
-	ListCell   *p;
 	Notification *n;
 
 	if (pendingNotifies == NIL)
@@ -2175,9 +2174,11 @@ AsyncExistsPendingNotify(const char *channel, const char *payload)
 	 * backwards in order to make duplicate-elimination a tad faster when the
 	 * same condition is signaled many times in a row. So as a compromise we
 	 * check the tail element first which we can access directly. If this
-	 * doesn't match, we check the whole list.
+	 * doesn't match, we used to check the whole list; we don't do that
+	 * anymore, because it was inefficient in the case when many distinct
+	 * channels are notified.
 	 *
-	 * As we are not checking our parents' lists, we can still get duplicates
+	 * Also, as we are not checking our parents' lists, we can get duplicates
 	 * in combination with subtransactions, like in:
 	 *
 	 * begin;
@@ -2192,15 +2193,6 @@ AsyncExistsPendingNotify(const char *channel, const char *payload)
 		strcmp(n->payload, payload) == 0)
 		return true;
 
-	foreach(p, pendingNotifies)
-	{
-		n = (Notification *) lfirst(p);
-
-		if (strcmp(n->channel, channel) == 0 &&
-			strcmp(n->payload, payload) == 0)
-			return true;
-	}
-
 	return false;
 }