Re: Wrong rows estimations with joins of CTEs slows queries by more than factor 500

From: vignesh C <vignesh21(at)gmail(dot)com>
To: Richard Guo <guofenglinux(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, 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: 2024-01-29 03:19:53
Message-ID: CALDaNm1Ti29941R6H+k0_hmgqFAJbhkXAAFSB+BJOwiATMnBrg@mail.gmail.com
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On Mon, 29 Jan 2024 at 08:01, Richard Guo <guofenglinux(at)gmail(dot)com> wrote:
>
>
> On Sat, Jan 27, 2024 at 10:08 AM vignesh C <vignesh21(at)gmail(dot)com> wrote:
>>
>> On Mon, 8 Jan 2024 at 22:21, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> >
>> > 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 have changed the status of the commitfest entry to "Committed" as I
>> noticed the patch has already been committed.
>
>
> Well, the situation seems a little complex here. At first, this thread
> was dedicated to discussing the 'Examine-simple-variable-for-Var-in-CTE'
> patch, which has already been pushed in [1]. Subsequently, I proposed
> another patch 'Propagate-pathkeys-from-CTEs-up-to-the-outer-query' in
> [2], which is currently under review and is what the commitfest entry
> for. Later on, within the same thread, another patch was posted as a
> fix to the first patch and was subsequently pushed in [3]. I believe
> this sequence of events might have led to confusion.
>
> What is the usual practice in such situations? I guess I'd better to
> fork a new thread to discuss my proposed patch which is about the
> 'Propagate-pathkeys-from-CTEs-up-to-the-outer-query'.

Sorry I missed to notice that there was one pending patch yet to be
committed, I feel you can continue discussing here itself just to
avoid losing any historical information about the issue and the
continuation of the discussion. You can add a new commitfest entry for
this.

Regards,
Vignesh

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