Horton

Re: POC: make mxidoff 64 bits

wenhui qiu <qiuwenhuifx@gmail.com>

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From: wenhui qiu <qiuwenhuifx@gmail.com>
To: Maxim Orlov <orlovmg@gmail.com>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Alexander Korotkov <aekorotkov@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Postgres hackers <pgsql-hackers@lists.postgresql.org>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Date: 2025-12-04T02:04:46Z
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 →

  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.

Hi
> 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.
Agree +1, If this had been done twenty years ago, the cost might have been
unacceptable. But with today’s hardware—especially disk random and
sequential I/O performance improving by hundreds of thousands of times, and
memory capacity increasing by several hundred times—it’s almost
unimaginable that we now have single 256-GB DIMMs. So this kind of overhead
is negligible for modern hardware.


Thanks


On Wed, 3 Dec 2025 at 17:54, Maxim Orlov <orlovmg@gmail.com> wrote:

> 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.
>