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Re: BUG #18885: ERROR: corrupt MVNDistinct entry - 2

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Tomas Vondra <tomas@vondra.me>
Cc: Andrei Lepikhov <lepihov@gmail.com>, tharakan@gmail.com, pgsql-bugs@lists.postgresql.org, PG Bug reporting form <noreply@postgresql.org>, Alexander Korotkov <aekorotkov@gmail.com>
Date: 2025-04-16T04:11:42Z
Lists: pgsql-bugs 
On Wed, 16 Apr 2025 at 01:16, Tomas Vondra <tomas@vondra.me> wrote:
> In any case, such rework seems out of scope for PG18 - it's much more
> than a fix for the bug.

This is the reason I stopped short of adjusting the code in the patch
I proposed in [1].  Speaking of which, do you have any views on that?
It seems much more likely that someone would have caught the issue
being reported here when writing the patch or during review if there
was some sort of documentation to mention the function can't handle
duplicate GroupVarInfos.

I'll look at that patch again in the next few days with aims to push
it unless someone has something to say about it.

David

[1] https://postgr.es/m/CAApHDvocZCUhM9W9mJ39d6oQz7ePKoqFnao_347mvC-A7QatcQ@mail.gmail.com

Commits

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

  1. Properly prepare varinfos in estimate_multivariate_bucketsize()

  2. Improve comments for estimate_multivariate_ndistinct()

  3. Use extended stats for precise estimation of bucket size in hash join

  4. Ignore nullingrels when looking up statistics