Horton

Re: improve performance of pg_dump with many sequences

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Euler Taveira <euler@eulerto.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2024-07-17T03:23:08Z
Lists: pgsql-hackers 
On Wed, Jul 17, 2024 at 11:30:04AM +0900, Michael Paquier wrote:
> Yeah, I have bumped on the same issue.  In the long term, I also think
> that we'd better have pg_sequence_last_value() return a row with
> is_called and the value scanned.  As you say, it won't help except
> when upgrading from versions of Postgres that are at least to v18,
> assuming that this change gets in the tree, but that would be much
> better in the long term and time flies fast.

AFAICT pg_sequence_last_value() is basically an undocumented internal
function only really intended for use by the pg_sequences system view, so
changing the function like this for v18 might not be out of the question.
Otherwise, I think we'd have to create a strikingly similar function with
slightly different behavior, which would be a bizarre place to end up.

-- 
nathan

Commits

  1. pg_dump: Fix gathering of sequence information.

  2. Improve performance of dumpSequence().

  3. Improve performance of dumpSequenceData().

  4. Introduce pg_sequence_read_tuple().

  5. Parse sequence type and integer metadata in dumpSequence().