COMMENT ON casts, conversions, languages, operator classes, and

large objects.  Dump all these in pg_dump; also add code to pg_dump
user-defined conversions.  Make psql's large object code rely on
the backend for inserting/deleting LOB comments, instead of trying to
hack pg_description directly.  Documentation and regression tests added.

Christopher Kings-Lynne, code reviewed by Tom

src/backend/storage/large_object/inv_api.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/large_object/inv_api.c,v 1.100 2003/11/12 21:15:54 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/large_object/inv_api.c,v 1.101 2003/11/21 22:32:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -31,12 +31,14 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_largeobject.h"
 #include "catalog/pg_type.h"
+#include "commands/comment.h"
 #include "libpq/libpq-fs.h"
 #include "miscadmin.h"
 #include "storage/large_object.h"
 #include "storage/smgr.h"
-#include "utils/fmgroids.h"
 #include "utils/builtins.h"
+#include "utils/fmgroids.h"
+#include "utils/lsyscache.h"
 
 
 static int32
@@ -174,8 +176,16 @@ inv_close(LargeObjectDesc *obj_desc)
 int
 inv_drop(Oid lobjId)
 {
+	Oid classoid;
+
 	LargeObjectDrop(lobjId);
 
+	/* pg_largeobject doesn't have a hard-coded OID, so must look it up */
+	classoid = get_system_catalog_relid(LargeObjectRelationName);
+
+	/* Delete any comments on the large object */
+	DeleteComments(lobjId, classoid, 0);
+
 	/*
 	 * Advance command counter so that tuple removal will be seen by later
 	 * large-object operations in this transaction.