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Re: Fix bug in multixact Oldest*MXactId initialization and access

Heikki Linnakangas <hlinnaka@iki.fi>

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From: Heikki Linnakangas <hlinnaka@iki.fi>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Yura Sokolov <y.sokolov@postgrespro.ru>, Sami Imseih <samimseih@gmail.com>, Chao Li <li.evan.chao@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2026-03-04T09:47:54Z
Lists: pgsql-hackers 
On 03/03/2026 20:47, Tom Lane wrote:
> Heikki Linnakangas <hlinnaka@iki.fi> writes:
>> On 03/03/2026 17:22, Tom Lane wrote:
>>> I wonder if we couldn't reduce future maintenance effort for
>>> prepared_xacts_1.out by modifying that test script to make an
>>> early exit if prepared transactions are disabled.
> 
>> +1, I was just thinking the same.
> 
> Personally I'd put the exit test after the file's header comment,
> but that's just a quibble.  LGTM otherwise.

Yeah I agree it would look a little neater, but I put the exit test 
first so that the comment doesn't get echoed to the output when the test 
isn't run. That way we don't need to remember to update 
prepared_xacts_1.out if we change the header comment. It hasn't changed 
for 20 years, but still :-).

Committed, thanks!

- Heikki

Commits

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

  1. Add test for row-locking and multixids with prepared transactions

  2. Skip prepared_xacts test if max_prepared_transactions < 2

  3. Fix OldestMemberMXactId and OldestVisibleMXactId array usage

  4. Redefine backend ID to be an index into the proc array

  5. Fix an old bug in multixact and two-phase commit. Prepared transactions can