| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | Andrei Lepikhov <lepihov(at)gmail(dot)com> |
| Cc: | Álvaro Herrera <alvherre(at)kurilemu(dot)de>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andy Fan <zhihuifan1213(at)163(dot)com>, wenhui qiu <qiuwenhuifx(at)gmail(dot)com> |
| Subject: | Re: Pathify RHS unique-ification for semijoin planning |
| Date: | 2025-09-03 09:12:53 |
| Message-ID: | CAMbWs4-UXdxMaZO-GgNx7Y4tWoDutc4uVmnhUBn+8afHp520og@mail.gmail.com |
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On Tue, Sep 2, 2025 at 7:56 PM Andrei Lepikhov <lepihov(at)gmail(dot)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
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