From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
cc: Alexander Lakhin <exclusion@gmail.com>, Jian Guo <gjian@vmware.com>,
        Tomas Vondra <tomas.vondra@enterprisedb.com>,
        Hans Buschmann <buschmann@nidsa.net>,
        "pgsql-hackers@lists.postgresql.org"
 <pgsql-hackers@lists.postgresql.org>,
        Zhenghua Lyu <zlyu@vmware.com>
Subject: Re: Wrong rows estimations with joins of CTEs slows queries by more
 than factor 500
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Comments: In-reply-to Richard Guo <guofenglinux@gmail.com>
	message dated "Mon, 08 Jan 2024 19:14:11 +0800"
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Date: Mon, 08 Jan 2024 11:51:22 -0500
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Richard Guo <guofenglinux@gmail.com> writes:
> On Sun, Jan 7, 2024 at 6:41 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Thanks for the report!  I guess we need something like the attached.

> +1.

Pushed, thanks for looking at it.

>> I'm surprised that this hasn't been noticed before; was the case
>> really unreachable before?

> It seems that this case is only reachable with Vars of an INSERT target
> relation, and it seems that there is no other way to reference such a
> Var other than using CTE.

I'm a little uncomfortable with that conclusion, but for the moment
I refrained from back-patching.  We can always add the patch to v16
later if we find it's not so unreachable.  (Before v16, there was
no find_base_rel here at all.)

			regards, tom lane