Re: pgsql: Doc: add information about partition locking

Hi David,

On Wed, Apr 2, 2025 at 10:03 AM David Rowley <drowley(at)postgresql(dot)org> wrote:
>
> Doc: add information about partition locking
>
> The documentation around locking of partitions for the executor startup
> phase of run-time partition pruning wasn't clear about which partitions
> were being locked. Fix that.
>
> Reviewed-by: Tender Wang <tndrwang(at)gmail(dot)com>
> Discussion: https://postgr.es/m/CAApHDvp738G75HfkKcfXaf3a8s%3D6mmtOLh46tMD0D2hAo1UCzA%40mail.gmail.com
> Backpatch-through: 13
>
> Branch
> ------
> master
>
> Details
> -------
> https://git.postgresql.org/pg/commitdiff/121d774caea4c93c8b36fb20a17ef774e60894d6

- <command>EXPLAIN</command> output.
+ <command>EXPLAIN</command> output. The query planner obtains locks for
+ all partitions which are part of the plan. However, when the executor
+ uses a cached plan, locks are only obtained on the partitions which
+ remain after partition pruning done during the initialization phase of
+ execution, i.e., the ones shown in the <command>EXPLAIN</command>
+ output and not the ones referred to by the
+ <quote>Subplans Removed</quote> property.
</para>
</listitem>

This text was correct when committed, but became incorrect after I
reverted 525392d57 in May 2025. Sorry for not catching it sooner.

I think we should change the text in both master and REL_18_STABLE to
match what you added in the older branches. I can change it back to
this when we get pruning-aware locking again.

--
Thanks, Amit Langote