Horton

Re: Oversight in reparameterize_path_by_child leading to executor crash

Andrei Lepikhov <a.lepikhov@postgrespro.ru>

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From: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
To: Richard Guo <guofenglinux@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2023-09-20T07:18:20Z
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 23/8/2023 12:37, Richard Guo wrote:
> If we go with the "tablesample scans can't be reparameterized" approach
> in the back branches, I'm a little concerned that what if we find more
> cases in the futrue where we need modify RTEs for reparameterization.
> So I spent some time seeking and have managed to find one: there might
> be lateral references in a scan path's restriction clauses, and
> currently reparameterize_path_by_child fails to adjust them.
It may help you somehow: in [1], we designed a feature where the 
partitionwise join technique can be applied to a JOIN of partitioned and 
non-partitioned tables. Unfortunately, it is out of community 
discussions, but we still support it for sharding usage - it is helpful 
for the implementation of 'global' tables in a distributed 
configuration. And there we were stuck into the same problem with 
lateral relids adjustment. So you can build a more general view of the 
problem with this patch.

[1] Asymmetric partition-wise JOIN
https://www.postgresql.org/message-id/flat/CAOP8fzaVL_2SCJayLL9kj5pCA46PJOXXjuei6-3aFUV45j4LJQ%40mail.gmail.com

-- 
regards,
Andrey Lepikhov
Postgres Professional