Improve pg_dump's query for retrieving BLOB comments to be more efficient

when there are many blobs and not so many comments.  Tamas Vincze

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index e4ea6eefa0510b4fd54fbecb4c89d103238b0caa..29335264c0133a7042d5042609a4802bb4e83fb0 100644 (file)
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -1995,7 +1995,13 @@ dumpBlobComments(Archive *AH, void *arg)
        selectSourceSchema("pg_catalog");
 
        /* Cursor to get all BLOB comments */
-       if (AH->remoteVersion >= 70200)
+       if (AH->remoteVersion >= 70300)
+               blobQry = "DECLARE blobcmt CURSOR FOR SELECT loid, "
+                                 "obj_description(loid, 'pg_largeobject') "
+                                 "FROM (SELECT DISTINCT loid FROM "
+                                 "pg_description d JOIN pg_largeobject l ON (objoid = loid) "
+                                 "WHERE classoid = 'pg_largeobject'::regclass) ss";
+       else if (AH->remoteVersion >= 70200)
                blobQry = "DECLARE blobcmt CURSOR FOR SELECT loid, "
                                  "obj_description(loid, 'pg_largeobject') "
                                  "FROM (SELECT DISTINCT loid FROM pg_largeobject) ss";