Horton

Re: Oversight in reparameterize_path_by_child leading to executor crash

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Richard Guo <guofenglinux@gmail.com>
Cc: Andrei Lepikhov <a.lepikhov@postgrespro.ru>, Alena Rybakina <lena.ribackina@yandex.ru>, Tom Lane <tgl@sss.pgh.pa.us>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2024-01-15T18:30:08Z
Lists: pgsql-hackers

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  1. Postpone reparameterization of paths until create_plan().

  2. Apply band-aid fix for an oversight in reparameterize_path_by_child.

On Mon, Jan 8, 2024 at 3:32 AM Richard Guo <guofenglinux@gmail.com> wrote:
> Thanks for the suggestion.  Attached is an updated patch which is added
> with a commit message that tries to explain the problem and the fix.

This is great. The references to "the sampling infos" are a little bit
confusing to me. I'm not sure if this is referring to
TableSampleClause objects or what.

> Fair point.  I think we can back-patch a more minimal fix, as Tom
> proposed in [1], which disallows the reparameterization if the path
> contains sampling info that references the outer rel.  But I think we
> need also to disallow the reparameterization of a path if it contains
> restriction clauses that reference the outer rel, as such paths have
> been found to cause incorrect results, or planning errors as in [2].

Do you want to produce a patch for that, to go along with this patch for master?

I know this is on Tom's to-do list which makes me a bit reluctant to
get too involved here, because certainly he knows this code better
than I do, maybe better than anyone does, but on the other hand, we
shouldn't leave server crashes unfixed for too long, so maybe I can do
something to help at least with that part of it.

-- 
Robert Haas
EDB: http://www.enterprisedb.com