Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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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>
Date: 2024-01-08T16:51:22Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Allow examine_simple_variable() to work on INSERT RETURNING Vars.

  2. Extract column statistics from CTE references, if possible.

  3. Remove SQL regression tests for GUCs related to NO_SHOW_ALL

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