public inbox for [email protected]  

help / color / mirror / Atom feed

From: Jeff Davis <[email protected]>
To: Bertrand Drouvot <[email protected]>
To: Heikki Linnakangas <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Roman Eskin <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Alexander Lakhin <[email protected]>
Cc: [email protected]
Cc: Tom Lane <[email protected]>
Subject: Re: Avoid orphaned objects dependencies, take 3
Date: Wed, 03 Jun 2026 11:08:13 -0700
Message-ID: <[email protected]> (raw)
In-Reply-To: <ah1PIyqtT+427dWb@bdtpg>
References: <CA+TgmoZh8yXoQ2AF-VFSTswhin0o+BZ78AaOsWZskCW1GHBd6g@mail.gmail.com>
	<[email protected]>
	<[email protected]>
	<ad/awXLnMuc6Rf5M@bdtpg>
	<afCXPVNuvpf5ECGZ@bdtpg>
	<CA+TgmobtzkG9HzGtDXbgb3KVE46qHuSvGcuKHgAGQ1aejCoLLw@mail.gmail.com>
	<agsCqlLTytZCudMv@bdtpg>
	<[email protected]>
	<ahYAKgbx05IQdjwR@bdtpg>
	<[email protected]>
	<ah1PIyqtT+427dWb@bdtpg>

On Mon, 2026-06-01 at 09:21 +0000, Bertrand Drouvot wrote:
> Now that we avoid orphaned objects dependencies, I resumed working on
> Robert's
> concern about the TOCTOU window where a REVOKE could land between the
> original
> permission check and the dependency recording.
> 
> Based on our discussion during PGConf.dev, PFA a new patch that uses
> the same
> approach as RangeVarGetRelidExtended(): record
> SharedInvalidMessageCounter at the
> time of the original aclcheck, then before locking compare the
> current counter to
> the saved value. If it changed, recheck permission before acquiring
> the lock.
> After the lock wait, if more invalidations arrived, release and
> retry.

RangeVarGetRelidExtended() coordinates three things:

  - name lookup
  - lock
  - ACL check

whereas recheckAclAndLock() only coordinates the latter two. That means
there can still be some strange failures, like:

  -- Session 1
  BEGIN;
  DROP SCHEMA s2;

  -- Session 2
  SET search_path=s2, s1;
  CREATE FUNCTION f() RETURNS INT LANGUAGE plpgsql AS
    $$ BEGIN RETURN 42; END; $$;

  -- Session 1
  COMMIT;

  -- Session 2
  ERROR:  referenced schema was concurrently dropped

even though no schema was actually referenced in the query, and a retry
of the transaction successfully creates the function in s1. Is that
expected?

Regards,
	Jeff Davis

view thread (50+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: Re: Avoid orphaned objects dependencies, take 3
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox