Horton

Re: The documentation for READ COMMITTED may be incomplete or wrong

Aleksander Alekseev <aleksander@timescale.com>

View thread View on postgr.es
From: Aleksander Alekseev <aleksander@timescale.com>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Amit Langote <amitlangote09@gmail.com>
Date: 2023-05-18T15:27:22Z
Lists: pgsql-hackers 
Hi,

> I wonder what we got wrong.

One thing we noticed is that the description for EvalPlanQual may be wrong [1]:

"""
In UPDATE/DELETE, only the target relation needs to be handled this way.
In SELECT FOR UPDATE, there may be multiple relations flagged FOR UPDATE,
so we obtain lock on the current tuple version in each such relation before
executing the recheck.
"""

[1]: https://github.com/postgres/postgres/blob/master/src/backend/executor/README#L381

-- 
Best regards,
Aleksander Alekseev

Commits

  1. Fix misbehavior of EvalPlanQual checks with multiple result relations.

  2. Rework planning and execution of UPDATE and DELETE.