From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
Cc: exclusion@gmail.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19037: Planner fails on estimating array length with "no relation entry" error
Date: Mon, 01 Sep 2025 10:57:37 -0400
Message-ID: <346889.1756738657@sss.pgh.pa.us> (raw)
In-Reply-To: <CAMbWs4_5Q3V_M1FavN07TxcOHhE38vtBaHs-LM2-RN=paYGi-g@mail.gmail.com>
References: <19037-3d1c7bb553c7ce84@postgresql.org>
<50858.1756590676@sss.pgh.pa.us>
<CAMbWs4_5Q3V_M1FavN07TxcOHhE38vtBaHs-LM2-RN=paYGi-g@mail.gmail.com>
Richard Guo <guofenglinux@gmail.com> writes:
> On Sun, Aug 31, 2025 at 6:51 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> The most expedient solution is probably to hack examine_variable
>> so that it doesn't fail if root->simple_rel_array isn't there yet.
>> That seems mighty ugly though.
> As an alternative, I wonder if we could pass root as NULL to
> cost_subplan() when it's called from build_subplan(), and possibly
> also from SS_process_ctes(). At those points, the root does not yet
> contain enough information to safely consult statistics. Meanwhile,
> cost_qual_eval() and the functions it calls are already well-equipped
> to handle a NULL root.
Good suggestion, that does seem more in keeping with established
hacks^H^H^Hpractice. It'll need some commentary about why.
I'm slightly tempted to do the dirty work in cost_subplan() itself,
ie pass a NULL down to cost_qual_eval from there. Right now it
doesn't matter, but maybe in future there would be some other
safer use for the parent root in cost_subplan()? This approach
would force the same behavior for the third caller of cost_subplan,
SS_make_initplan_from_plan. But I don't think it matters there,
since an initplan will by definition not be consulting anything from
the parent plan.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, guofenglinux@gmail.com, exclusion@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19037: Planner fails on estimating array length with "no relation entry" error
In-Reply-To: <346889.1756738657@sss.pgh.pa.us>
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