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Re: pg_upgrade failing for 200+ million Large Objects

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Jan Wieck <jan@wi3ck.info>, Magnus Hagander <magnus@hagander.net>, Robins Tharakan <tharakan@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2021-03-20T16:45:36Z
Lists: pgsql-hackers 
On Sat, Mar 20, 2021 at 11:23:19AM -0400, Tom Lane wrote:
> I wonder if pg_dump could improve matters cheaply by aggregating the
> large objects by owner and ACL contents.  That is, do
> 
> select distinct lomowner, lomacl from pg_largeobject_metadata;
> 
> and make just *one* BLOB TOC entry for each result.  Then dump out
> all the matching blobs under that heading.
> 
> A possible objection is that it'd reduce the ability to restore blobs
> selectively, so maybe we'd need to make it optional.
> 
> Of course, that just reduces the memory consumption on the client
> side; it does nothing for the locks.  Can we get away with releasing the
> lock immediately after doing an ALTER OWNER or GRANT/REVOKE on a blob?

Well, in pg_upgrade mode you can, since there are no other cluster
users, but you might be asking for general pg_dump usage.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.

Commits

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

  1. Count individual SQL commands in pg_restore's --transaction-size mode.

  2. Reduce number of commands dumpTableSchema emits for binary upgrade.

  3. Invent --transaction-size option for pg_restore.

  4. Rearrange pg_dump's handling of large objects for better efficiency.

  5. Add temporal PRIMARY KEY and UNIQUE constraints

  6. Fix typo and case in messages