Horton

Re: add function for creating/attaching hash table in DSM registry

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Sami Imseih <samimseih@gmail.com>
Cc: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>, pgsql-hackers@postgresql.org
Date: 2025-06-10T16:21:37Z
Lists: pgsql-hackers

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On Tue, Jun 10, 2025 at 10:38:29AM -0500, Nathan Bossart wrote:
> On Mon, Jun 09, 2025 at 07:14:28PM -0500, Sami Imseih wrote:
>> Going back to the original point, DSMRegistryHash and DSMRegistryHash
>> are built-in, and those names are well-defined and actually refer to
>> waits related to the mechanism of registering a DSA or a HASH.
>> I think it will be odd to append "_dsh", but we should at minimum add
>> a comment in the GetNamedDSMHash explaining this.
> 
> This should be addressed in v3.
> 
> I'm not quite following your uneasiness with the tranche names.  For the
> dshash table, we'll need a tranche for the DSA and one for the hash table,
> so presumably any wait events for those locks should be named accordingly,
> right?

Unrelated, but it'd probably be a good idea to make sure the segment is
initialized instead of assuming it'll be zeroed out (and further assuming
that DSHASH_HANDLE_INVALID is 0)...

-- 
nathan

Commits

  1. Fix cross-version upgrade test breakage from commit fe07100e82.

  2. Add GetNamedDSA() and GetNamedDSHash().

  3. Remove dynamic_shared_memory_type=none

  4. Introduce dynamic shared memory areas.

  5. Relax the requirement that all lwlocks be stored in a single array.