--- postgresql-8.3.7/src/bin/pg_dump/pg_dump.c.orig	2009-03-31 15:47:28.000000000 -0400
+++ postgresql-8.3.7/src/bin/pg_dump/pg_dump.c	2009-04-01 10:25:39.000000000 -0400
@@ -1759,7 +1759,13 @@
 
 	/* Cursor to get all BLOB comments */
 	if (AH->remoteVersion >= 70200)
-		blobQry = "DECLARE blobcmt CURSOR FOR SELECT loid, obj_description(loid, 'pg_largeobject') FROM (SELECT DISTINCT loid FROM pg_largeobject) ss";
+		/* Get comments for BLOBs that have a matching pg_description row. When there are many
+		 * (millions) of BLOBs without comments this avoids fetching and then ignoring them,
+		 * potentionally saving hours of backup time.
+		 * Note that it may still select BLOBs that have no comment if a pg_description row's objoid
+		 * matches a BLOB's loid, but references an object contained in a different system catalog,
+		 * thus the PQgetisnull() check below is still needed to ignore them. */
+		blobQry = "DECLARE blobcmt CURSOR FOR SELECT loid, obj_description(loid, 'pg_largeobject') FROM (SELECT DISTINCT loid FROM pg_description JOIN pg_largeobject ON (pg_description.objoid = pg_largeobject.loid)) ss";
 	else if (AH->remoteVersion >= 70100)
 		blobQry = "DECLARE blobcmt CURSOR FOR SELECT loid, obj_description(loid) FROM (SELECT DISTINCT loid FROM pg_largeobject) ss";
 	else