Horton

Re: strange perf regression with data checksums

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Tomas Vondra <tomas@vondra.me>
Cc: Aleksander Alekseev <aleksander@timescale.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2025-06-04T17:39:40Z
Lists: pgsql-hackers

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On Wed, Jun 4, 2025 at 10:21 AM Peter Geoghegan <pg@bowt.ie> wrote:
> On Wed, Jun 4, 2025 at 7:33 AM Tomas Vondra <tomas@vondra.me> wrote:
> > So better to get this in now, otherwise we may have to wait until PG19,
> > because of ABI (the patch adds a field into BTScanPosData, but maybe
> > it'd be possible to add it into padding, not sure).
>
> I agree. I can get this into shape for commit today.

Attached is v3, which is functionally the same as v2. It has improved
comments, and a couple of extra assertions. Plus there's a real commit
message now.

I also relocated the code that sets so.drop_pin from
_bt_preprocess_keys to btrescan. That seems like the more logical
place for it.

My current plan is to commit this in the next couple of days.

-- 
Peter Geoghegan

Commits

  1. Make _bt_killitems drop pins it acquired itself.

  2. Avoid BufferGetLSNAtomic() calls during nbtree scans.

  3. Reduce pinning and buffer content locking for btree scans.