(2010/02/09 20:16), Takahiro Itagaki wrote:
>
> KaiGai Kohei<kaigai@ak.jp.nec.com> wrote:
>
>>> I don't think this is necessarily a good idea. We might decide to treat
>>> both things separately in the future and it having them represented
>>> separately in the dump would prove useful.
>>
>> I agree. From design perspective, the single section approach is more
>> simple than dual section, but its change set is larger than the dual.
>
> OK.
>
>
> When I tested a custom dump with pg_restore, --clean& --single-transaction
> will fail with the new dump format because it always call lo_unlink()
> even if the large object doesn't exist. It comes from dumpBlobItem:
>
> ! dumpBlobItem(Archive *AH, BlobInfo *binfo)
> ! appendPQExpBuffer(dquery, "SELECT lo_unlink(%s);\n", binfo->dobj.name);
>
> The query in DropBlobIfExists() could avoid errors -- should we use it here?
> | SELECT lo_unlink(oid) FROM pg_largeobject_metadata WHERE oid = %s;
Yes, we can use this query to handle --clean option.
I'll fix it soon.
> BTW, --clean option is ambiguous if combined with --data-only. Restoring
> large objects fails for the above reason if previous objects don't exist,
> but table data are restored *without* truncation of existing data. Will
> normal users expect TRUNCATE-before-load for --clean& --data-only cases?
>
> Present behaviors are;
> Table data - Appended. (--clean is ignored)
> Large objects - End with an error if object doesn't exist.
> IMO, ideal behaviors are:
> Table data - Truncate existing data and load new ones.
> Large objects - Work like as MERGE (or REPLACE, UPSERT).
>
> Comments?
In the existing "BLOBS" section, it creates and restores large objects
in same time. And, it also unlink existing large object (if exists)
just before restoring them, when --clean is given.
In my opinion, when --clean is given, it also should truncate the table
before restoring, even if --data-only is co-given.
Thanks,
--
KaiGai Kohei <kaigai@kaigai.gr.jp>
