Re: POC: make mxidoff 64 bits

Maxim Orlov <orlovmg@gmail.com>

From: Maxim Orlov <orlovmg@gmail.com>

To: Heikki Linnakangas <hlinnaka@iki.fi>

Cc: Alexander Korotkov <aekorotkov@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, wenhui qiu <qiuwenhuifx@gmail.com>, Postgres hackers <pgsql-hackers@lists.postgresql.org>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>

Date: 2025-12-03T09:54:23Z

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

The biggest problem with compression, in my opinion, is that losing
even one byte causes the loss of the entire compressed block in the
worst case scenario. After all, we still don't have checksums for the
SLRU's, which is a shame by itself.

Again, I'm not against the idea of compression, but the risks need to
be considered.

As a software developer, I definitely want to implement compression and
save a few gigabytes. However, given my previous experience using
Postgres in real-world applications, reliability at the cost of several
gigabytes would not have caused me any trouble. Just saying.

-- 
Best regards,
Maxim Orlov.