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Re: Make tuple deformation faster

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Andres Freund <andres@anarazel.de>, Matthias van de Meent <boekewurm+postgres@gmail.com>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2025-03-05T12:07:21Z
Lists: pgsql-hackers

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On Wed, 5 Mar 2025 at 08:48, Jeff Davis <pgsql@j-davis.com> wrote:
> I happened to run into the code and was surprised to see a strongly-
> worded comment about the size of CompactAttribute, but then also see
> independent booleans rather than flags or bitfields.
>
> Did the discussion end here, or was there some kind of conclusion? Is
> it worth adding a comment about why we use independent booleans, even
> if we don't have a complete answer?

I must have either forgotten to try that, or I tried it and wrote it
off and forgot to document it.

Anyway, I've now benchmarked using bitfields on the same 3 machines
that I used last time. There are certainly some cases where it's
faster with the bitfields, but it's mainly slower.

I've attached the results. The 3990x with clang looks good, but the
rest are mostly slower.

David

Commits

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

  1. Fix possible Assert failure in verify_compact_attribute()

  2. Speedup tuple deformation with additional function inlining

  3. Fix race condition in TupleDescCompactAttr assert code

  4. Optimize alignment calculations in tuple form/deform

  5. Remove pg_attribute.attcacheoff column

  6. Introduce CompactAttribute array in TupleDesc, take 2

  7. Introduce CompactAttribute array in TupleDesc

  8. Use TupleDescAttr macro consistently