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

Hi Nathan,

>
> I like this idea, but I took it one step further in the attached patch and
> made the registry entry struct flexible enough to store any type of entry.
> Specifically, I've added a new "type" enum followed by a union of the
> different structs used to store the entry data. I was originally trying to
> avoid this kind of invasive change, but it's not nearly as complicated as I
> feared, and there are benefits such as fewer shared memory things to juggle
> and better sanity checking. It should also be easy to extend in the
> future. WDYT?
>
>

Thank you for implementing these changes.
The improvements look good and enhance the feature's utility. I have
already started incorporating
GetNamedDSA into my code to display memory context statistics.

A potential future enhancement could be allowing GetNamedDSHASH to accept
an existing DSA name.
This would enable the DSHASH to reuse a DSA area instead of creating a new
one each time.
I plan to use this registry to store DSA pointers that all belong to the
same DSA area, and this enhancement
would be particularly beneficial. If you find this idea useful, I would be
interested in working on it.

Thank you,
Rahila Syed