Re: Fwd: dsm_registry: Add detach and destroy features

On Mon, Jun 16, 2025 at 09:02:22AM +0900, Sungwoo Chang wrote:
> 2025년 6월 14일 (토) 오전 6:50, Nathan Bossart <nathandbossart@gmail.com>님이 작성:
>> Could your use-case be handled with a DSA?  On the other thread [0], we're
>> talking about adding a GetNamedDSA() function, which returns a DSA that you
>> can use to allocate and free shared memory as needed.  In theory you could
>> even detach the DSA if you no longer needed it in a backend, although
>> that's probably unnecessary.
> 
> My use-case requires access to the shared memory object through a named key.
> Even if we migrate the code to NamedDSA, within the DSA we will need some sort
> of a map between the named key and the object to access. So, I think NamedDSA
> won't be the solution.

Right, you'd need some other shared space for the DSA pointers.  In the
other thread, I'm using a dshash table (created via GetNamedDSMHash()) to
store those for test_dsm_registry [0].  There are probably other ways to do
this.

> How about when we call destroy, we check if there are other processes
> attached to it and if so, we throw an exception? I checked C++ boost
> interprocess library [0], and it looks like that's the way boost does.
> This way, we can avoid the aforementioned "partitioned" scenario.

That might work.

[0] https://postgr.es/m/aEyX-9k5vlK2lxjz%40nathan

-- 
nathan