Re: Horribly slow pg_upgrade performance with many Large Objects

Nathan Bossart <nathandbossart@gmail.com>

From: Nathan Bossart <nathandbossart@gmail.com>

To: Hannu Krosing <hannuk@google.com>

Cc: Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2025-07-08T21:06:16Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

pg_upgrade: Use COPY for large object metadata.
- 161a3e8b682e 19 (unreleased) landed
pg_dump: Fix object-type sort priority for large objects.
- fb6c860bbd1f 19 (unreleased) landed
- e43fae199e50 17.6 landed
- 36026b0fe3ab 18.0 landed
pg_upgrade: Mention that we preserve database OIDs in a comment.
- e2665efd0f4d 18.0 landed
pg_upgrade: Preserve database OIDs.
- aa01051418f1 15.0 cited
Fix pg_upgrade for oid removal.
- 12a53c732ced 12.0 cited

On Sun, Jul 06, 2025 at 02:48:08PM +0200, Hannu Krosing wrote:
> Did a quick check of the patch and it seems to work ok.

Thanks for taking a look.

> What do you think of the idea of not dumping pg_shdepend here, but
> instead adding the required entries after loading
> pg_largeobject_metadata based on the contents of it ?

While not dumping it might save a little space during upgrade, the query
seems to be extremely slow.  So, I don't see any strong advantage.

-- 
nathan