Horton

Re: POC: make mxidoff 64 bits

Heikki Linnakangas <hlinnaka@iki.fi>

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From: Heikki Linnakangas <hlinnaka@iki.fi>
To: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Maxim Orlov <orlovmg@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Alexander Korotkov <aekorotkov@gmail.com>, wenhui qiu <qiuwenhuifx@gmail.com>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-12-03T19:12:40Z
Lists: pgsql-hackers

Commits

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

  1. Fix partial read handling in pg_upgrade's multixact conversion

  2. Increase timeout in multixid_conversion upgrade test

  3. Improve sanity checks on multixid members length

  4. Clarify comment on multixid offset wraparound check

  5. Never store 0 as the nextMXact

  6. Add runtime checks for bogus multixact offsets

  7. Widen MultiXactOffset to 64 bits

  8. Move pg_multixact SLRU page format definitions to a separate header

  9. Convert confusing macros in multixact.c to static inline functions

  10. Index SLRUs by 64-bit integers rather than by 32-bit integers

  11. Cope with possible failure of the oldest MultiXact to exist.

On 01/12/2025 14:35, Ashutosh Bapat wrote:
> On Mon, Dec 1, 2025 at 2:23 PM Maxim Orlov <orlovmg@gmail.com> wrote:
>> On Fri, 28 Nov 2025 at 16:17, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> wrote:
>>> An UPDATE waits for FOR SHARE query to finish, and vice versa. In my
>>> experiments I didn't see an UPDATE creating a multi-xact. Why do we
>>> have UPDATEs in the load created by the test? Am I missing something?
>>
>> As far as I remember, this was done on purpose to create different
>> multixact members statuses randomly.
> 
> In that case, better to include that in the comments.

I think that was indeed the purpose, but the test should use FOR KEY 
SHARE rather than FOR SHARE. Otherwise the UPDATEs don't generate multixids.

- Heikki