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Re: Better shared data structure management and resizable shared data structures

Heikki Linnakangas <hlinnaka@iki.fi>

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From: Heikki Linnakangas <hlinnaka@iki.fi>
To: Matthias van de Meent <boekewurm+postgres@gmail.com>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>, chaturvedipalak1911@gmail.com
Date: 2026-04-05T23:28:47Z
Lists: pgsql-hackers 
On 05/04/2026 23:06, Heikki Linnakangas wrote:
> Here's patch version 12 [*]. I believe I've addressed all the feedback, 
> and I feel this is in pretty good shape now. There hasn't been any big 
> design changes lately.
> 
> One notable change is that I replaced the separate {request|init|attach} 
> _fn_arg fields in ShmemCallbacks with a single 'opaque_arg' field, and 
> added a brief comment to it. You both commented on whether we need that 
> at all, and maybe you're right that we don't, but at least it's now just 
> one field rather than three. As before, callers can simply ignore it if 
> they don't need it.

After another round of comment cleanups and such, committed. Thanks!

- Heikki

Commits

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

  1. Tidy up #ifdef USE_INJECTION_POINTS guards

  2. Convert all remaining subsystems to use the new shmem allocation API

  3. Convert buffer manager to use the new shmem allocation functions

  4. Add alignment option to ShmemRequestStruct()

  5. Convert AIO to use the new shmem allocation functions

  6. Convert SLRUs to use the new shmem allocation functions

  7. Refactor shmem initialization code in predicate.c

  8. Use the new shmem allocation functions in a few core subsystems

  9. Convert lwlock.c to use the new shmem allocation functions

  10. Introduce a registry of built-in shmem subsystems

  11. Convert pg_stat_statements to use the new shmem allocation functions

  12. Add a test module to test after-startup shmem allocations

  13. Introduce a new mechanism for registering shared memory areas

  14. Move some code from shmem.c and shmem.h

  15. Improve test_lwlock_tranches

  16. Test pg_stat_statements across crash restart

  17. Refactor PredicateLockShmemInit to not reuse var for different things

  18. Refactor ShmemIndex initialization

  19. Add a new shmem_request_hook hook.