Re: pg_plan_advice

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Ajay Pal <ajay(dot)pal(dot)k(at)gmail(dot)com>
Cc: Alexandra Wang <alexandra(dot)wang(dot)oss(at)gmail(dot)com>, Richard Guo <guofenglinux(at)gmail(dot)com>, Lukas Fittl <lukas(at)fittl(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jacob Champion <jacob(dot)champion(at)enterprisedb(dot)com>, Dian Fay <di(at)nmfay(dot)com>, Matheus Alcantara <matheusssilv97(at)gmail(dot)com>, Jakub Wartak <jakub(dot)wartak(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: pg_plan_advice
Date: 2026-02-12 13:08:16
Message-ID: CA+TgmoYg8Ft9CZWD2GVGn1Qt6EQTuHUuG_MkDaQ6XGD1doTK0w@mail.gmail.com
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On Thu, Feb 12, 2026 at 6:41 AM Ajay Pal <ajay(dot)pal(dot)k(at)gmail(dot)com> wrote:
> pg_plan_advice failed to match JOIN_ORDER advice because the genetic
> algorithm never attempts the specific join path requested.

Seems expected. It is bad if using GEQO results in a crash or if the
advice cause the expected outcome when the path is considered, but if
the randomness of GEQO causes it not to consider the path the user
wants, then the user either needs to stop using GEQO, or use
less-strict plan advice, or just understand that this kind of outcome
is a possibility.

Thanks,

--
Robert Haas
EDB: http://www.enterprisedb.com

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