Re: Pathify RHS unique-ification for semijoin planning

Richard Guo <guofenglinux@gmail.com>

From: Richard Guo <guofenglinux@gmail.com>

To: Andrei Lepikhov <lepihov@gmail.com>

Cc: Álvaro Herrera <alvherre@kurilemu.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>, Andy Fan <zhihuifan1213@163.com>, wenhui qiu <qiuwenhuifx@gmail.com>

Date: 2025-09-03T09:12:53Z

Lists: pgsql-hackers

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Simplify relation_has_unique_index_for()
- bf9ee294e567 19 (unreleased) landed
Pathify RHS unique-ification for semijoin planning
- 24225ad9aafc 19 (unreleased) landed
Convert varatt.h access macros to static inline functions.
- e035863c9a04 19 (unreleased) cited
Re-export a few of createplan.c's make_xxx() functions.
- 570be1f73f38 9.6.0 cited

On Tue, Sep 2, 2025 at 7:56 PM Andrei Lepikhov <lepihov@gmail.com> wrote:
> No questions, it is good enough optimisation. I'm worried only about
> implementation: It creates one more RelOptInfo that may look like a
> baserel, but we can't find it by find_base_rel or even find_join_rel. It
> seems a little inconsistent to me.
> Don't think it is critical - just complicates life for extension
> developers in some cases.

The RelOptInfo representing the unique-ified rel is intended to be
used only internally during path generation for semi-joins, and should
be opaque outside of that.  I don't think extensions should know about
it.

- Richard