Takahiro Itagaki wrote:
> KaiGai Kohei <kaigai@ak.jp.nec.com> wrote:
>
>>>> We have to reference pg_largeobject_metadata to check whether a certain
>>>> large objct exists, or not.
>> It is a case when we create a new large object, but write nothing.
>
> OK, that makes sense.
>
> In addition of the patch, we also need to fix pg_restore with
> --clean option. I added DropBlobIfExists() in pg_backup_db.c.
>
> A revised patch attached. Please check further mistakes.
+ void
+ DropBlobIfExists(ArchiveHandle *AH, Oid oid)
+ {
+ const char *lo_relname;
+ const char *lo_colname;
+
+ if (PQserverVersion(AH->connection) >= 80500)
+ {
+ lo_relname = "pg_largeobject_metadata";
+ lo_colname = "oid";
+ }
+ else
+ {
+ lo_relname = "pg_largeobject";
+ lo_colname = "loid";
+ }
+
+ /* Call lo_unlink only if exists to avoid not-found error. */
+ ahprintf(AH, "SELECT CASE WHEN EXISTS(SELECT 1 FROM pg_catalog.%s WHERE %s = '%u') THEN pg_catalog.lo_unlink('%u')
END;\n",
+ lo_relname, lo_colname, oid, oid);
+ }
I think the following approach is more reasonable for the current design.
if (PQserverVersion(AH->connection) >= 80500) { /* newer query */ ahprintf(AH, "SELECT
pg_catalog.lo_unlink(oid)" "FROM pg_catalog.pg_largeobject_metadata " "WHERE oid =
%u;\n",oid); } else { /* original query */ ahprintf(AH, "SELECT CASE WHEN EXISTS(SELECT 1 FROM
pg_catalog.pg_largeobjectWHERE loid = '%u') " "THEN pg_catalog.lo_unlink('%u') END;\n", oid, oid);
}
We don't have any reason why still CASE ... WHEN and subquery for the given
LOID. Right?
The fix-lo-contrib.patch looks good for me.
> BTW, we can optimize lo_truncate because we allow metadata-only large
> objects. inv_truncate() doesn't have to update the first data tuple to
> be zero length. It only has to delete all corresponding tuples like as:
> DELETE FROM pg_largeobject WHERE loid = {obj_desc->id}
Right, when inv_truncate takes an aligned length by LOBLKSIZE.
I'll also submit a small patch on CF-Jan, OK?
Thanks,
--
KaiGai Kohei <kaigai@kaigai.gr.jp>
