| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Make tuple deformation faster |
| Date: | 2025-03-05 12:07:21 |
| Message-ID: | CAApHDvq5ygT12jyfpj_JuSZ8T9-QtE9LhCsC51mELbbs__uVfA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, 5 Mar 2025 at 08:48, Jeff Davis <pgsql(at)j-davis(dot)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
| Attachment | Content-Type | Size |
|---|---|---|
| deform_test.sh.txt | text/plain | 1.1 KB |
| shrink_CompactAttribute.patch | application/x-patch | 1.3 KB |
| bitfields_gcc.png | image/png | 169.7 KB |
| bitfields_clang.png | image/png | 229.6 KB |
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