Horton

Re: Pathify RHS unique-ification for semijoin planning

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Álvaro Herrera <alvherre@kurilemu.de>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>, Andy Fan <zhihuifan1213@163.com>, wenhui qiu <qiuwenhuifx@gmail.com>
Date: 2025-07-24T03:40:50Z
Lists: pgsql-hackers

Commits

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  1. Simplify relation_has_unique_index_for()

  2. Pathify RHS unique-ification for semijoin planning

  3. Convert varatt.h access macros to static inline functions.

  4. Re-export a few of createplan.c's make_xxx() functions.

On Wed, Jul 23, 2025 at 5:11 PM Álvaro Herrera <alvherre@kurilemu.de> wrote:
> As a very trivial test on this patch, I ran the query in your opening
> email, both with and without the patch, scaling up the size of the table
> a little bit.

> This is a really nice improvement.  I think we could find queries that
> are arbitrarily faster, by feeding enough tuples to the unnecessary Sort
> nodes.

Thank you for testing this patch!

In addition to eliminating unnecessary sort nodes, this patch also
allows us to exploit pre-sorted paths that aren't necessarily the
cheapest total during the unique-ification step.  It also allows the
use of parallel plans for that step on large tables.  I think we could
also find queries that become faster as a result of these improvements.

Thanks
Richard