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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: 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: 2026-03-26T10:10:41Z
Lists: pgsql-hackers 
On 24/03/2026 17:32, Ashutosh Bapat wrote:
> 0002
> void
> InitShmemAllocator(PGShmemHeader *seghdr)
> {
> 
> The new ShmemIndex initialization code is cleaner and more
> straightforward. It avoids the recursive nature of ShmemInitHash.
> However with this change it's hard to keep track of all the
> initialization steps and their dependencies. Attached is a patch that
> makes small adjustments to the code to make it more clear.
> 
> Use of variable hash_size is actually misleading since it's not the
> size of the hash table but the expected/max number of entries in it.
> Removing it makes code more readable.

Thanks, committed this 0002 patch with those changes, to get that out of 
the way.

- 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.