Re: POC: make mxidoff 64 bits
Maxim Orlov <orlovmg@gmail.com>
From: Maxim Orlov <orlovmg@gmail.com>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: wenhui qiu <qiuwenhuifx@gmail.com>,
Alexander Korotkov <aekorotkov@gmail.com>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-11-07T16:03:11Z
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 →
-
Fix partial read handling in pg_upgrade's multixact conversion
- ac94ce8194e5 19 (unreleased) landed
-
Increase timeout in multixid_conversion upgrade test
- bd43940b02b2 19 (unreleased) landed
-
Improve sanity checks on multixid members length
- ecb553ae8211 19 (unreleased) landed
-
Clarify comment on multixid offset wraparound check
- 170361d7b869 14.21 landed
- b0b52b7123ae 15.16 landed
- 7d42e2367c6b 16.12 landed
- cd1a887fe9bf 17.8 landed
- 3fbad030a24d 18.2 landed
- 366dcdaf5779 19 (unreleased) landed
-
Never store 0 as the nextMXact
- 87a350e1f284 19 (unreleased) landed
-
Add runtime checks for bogus multixact offsets
- d4b7bde4183b 19 (unreleased) landed
-
Widen MultiXactOffset to 64 bits
- bd8d9c9bdfa0 19 (unreleased) landed
-
Move pg_multixact SLRU page format definitions to a separate header
- bb3b1c4f6462 19 (unreleased) landed
-
Convert confusing macros in multixact.c to static inline functions
- 0099b9408e8c 17.0 landed
-
Index SLRUs by 64-bit integers rather than by 32-bit integers
- 4ed8f0913bfd 17.0 cited
-
Cope with possible failure of the oldest MultiXact to exist.
- b6a3444fa635 9.4.4 cited
I noticed one minor issue after I had already sent the
previous letter.
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -1034,7 +1034,7 @@ GetNewMultiXactId(int nmembers, MultiXactOffset
*offset)
if (nextOffset + nmembers < nextOffset)
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
- "MultiXact members would wrap around"));
+ errmsg("MultiXact members would wrap around")));
*offset = nextOffset;
$ $PGBINOLD/pg_controldata -D pgdata
pg_control version number: 1800
Catalog version number: 202510221
...
Latest checkpoint's NextMultiXactId: 10000000
Latest checkpoint's NextMultiOffset: 999995050
Latest checkpoint's oldestXID: 748
...
I tried finding out how long it would take to convert a big number of
segments. Unfortunately, I only have access to a very old machine right
now. It took me 7 hours to generate this much data on my old
Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz with 16 Gb of RAM.
Here are my rough measurements:
HDD
$ sudo sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
$ time pg_upgrade
...
real 4m59.459s
user 0m19.974s
sys 0m13.640s
SSD
$ sudo sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
$ time pg_upgrade
...
real 4m52.958s
user 0m19.826s
sys 0m13.624s
I aim to get access to more modern stuff and check it all out there.
--
Best regards,
Maxim Orlov.