Re: Add 64-bit XIDs into PostgreSQL 15

Pavel Borisov <pashkin.elfe@gmail.com>

From: Pavel Borisov <pashkin.elfe@gmail.com>

To: "Finnerty, Jim" <jfinnert@amazon.com>

Cc: Simon Riggs <simon.riggs@enterprisedb.com>, Maxim Orlov <orlovmg@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>

Date: 2022-01-14T19:38:46Z

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 →

Add SLRU tests for 64-bit page case
- a60b8a58f435 17.0 landed
Make use FullTransactionId in 2PC filenames
- 5a1dfde8334b 17.0 landed
Use larger segment file names for pg_notify
- 2cdf131c46e6 17.0 landed
Index SLRUs by 64-bit integers rather than by 32-bit integers
- 4ed8f0913bfd 17.0 landed

Attachments

v6-0003-README-for-64bit-xid.patch (application/octet-stream) patch v6-0003

>
> We intend to do the following work on the patch soon:
> 1. Write a detailed README
> 2. Split the patch into several pieces including a separate part for
> XID_FMT. But if committers meanwhile choose to commit Jim's XID_FMT patch
> we also appreciate this and will rebase our patch accordingly.
>      2A. Probably refactor it to store precalculated XMIN/XMAX in memory
> tuple representation instead of t_xid_base/t_multi_base
>      2B. Split the in-memory part of a patch as a separate
> 3. Construct some variants for leaving "double xmax" format as a temporary
> one just after upgrade for having only one persistent on-disk format
> instead of two.
>      3A. By using SQL function "vacuum doublexmax;"
> OR
>      3B. By freeing space on all heap pages for pd_special before
> pg-upgrade.
> OR
>      3C. By automatically repacking all "double xmax" pages after upgrade
> (with a priority specified by common vacuum-related GUCs)
> 4. Intentionally prohibit starting a new transaction with XID difference
> of more than 2^32 from the oldest currently running one. This is to enforce
> some dba's action for cleaning defunct transaction but not binding one:
> he/she can wait if they consider these old transactions not defunct.
> 5. Investigate and add a solution for archs without 64-bit atomic values.
>        5A. Provide XID 8-byte alignment for systems where 64-bit atomics
> is provided for 8-byte aligned values.
>        5B. Wrap XID reading into PG atomic locks for remaining 32-bit ones
> (they are expected to be rare).
>

Hi, hackers!

PFA patch with README for 64xid proposal. It is 0003 patch of the same v6,
that was proposed earlier [1].
As always, I very much appreciate your ideas on this readme patch, on
overall 64xid patch [1], and on the roadmap on its improvement quoted above.

 [1]
https://www.postgresql.org/message-id/CACG%3DezZe1NQSCnfHOr78AtAZxJZeCvxrts0ygrxYwe%3DpyyjVWA%40mail.gmail.com

-- 
Best regards,
Pavel Borisov

Postgres Professional: http://postgrespro.com <http://www.postgrespro.com>