| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Richard Guo <guofenglinux(at)gmail(dot)com> |
| Cc: | Alexander Lakhin <exclusion(at)gmail(dot)com>, Jian Guo <gjian(at)vmware(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Hans Buschmann <buschmann(at)nidsa(dot)net>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Zhenghua Lyu <zlyu(at)vmware(dot)com> |
| Subject: | Re: Wrong rows estimations with joins of CTEs slows queries by more than factor 500 |
| Date: | 2024-01-08 16:51:22 |
| Message-ID: | 1941515.1704732682@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Richard Guo <guofenglinux(at)gmail(dot)com> writes:
> On Sun, Jan 7, 2024 at 6:41 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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
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