Re: Use CompactAttribute more often, when possible

> On Oct 20, 2025, at 12:46, David Rowley <dgrowleyml@gmail.com> wrote:
>
> 5983a4cff added CompactAttribute to TupleDesc to allow commonly
> accessed fields from the FormData_pg_attribute array to be accessed
> more quickly by having to load fewer cachelines from memory. That
> commit also went around and changed many locations to use
> CompactAttribute, but not all locations.
>
> The attached aims to adjust the remaining locations that I'm
> comfortable changing. I've avoided doing anything in tablecmds.c as
> that's where TupleDescs tend to get changed and I think there's a bit
> of undue risk using CompactAttribute there, just in case it gets
> accessed after the TupleDesc is changed and before flushing the
> pending changes to CompactAttribute in populate_compact_attribute().
>
> Also, I'm aware that the code around the population of the
> CompactAttribute has changed a bit since it was added. attgenerated no
> longer mirrors its equivalent pg_attribute column. If that was made to
> mirror that column again, then there are a few extra locations that
> could be made to use CompactAttribute. There's also some more
> complexity around CompactAttribute.attnotnull that's crept in. I think
> I roughly understand the need for that, but the intent of
> CompactAttribute mirroring commonly used pg_attribute fields is made
> no longer true by those changes as it now contains extra information
> that's unavailable in pg_attribute. It'd be nice if pg_attribute also
> had the various additional states of attnotnull that CompactAttribute
> now has. </rant>
>
> I don't think the attached is very interesting to look at, but l'll
> leave it here for a bit just in case anyone wants to look. Otherwise,
> I plan to just treat it as a follow-up of 5983a4cff.
>
> David
> <v1-0001-Use-CompactAttribute-more-often-when-possible.patch>

It’s good to learn. I wasn’t aware of CompactAttribute before.

I search for “TupleDescAttr”, and found more occurrences to replace. See the attached diff file.

--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/