Re: Support to define custom wait events for extensions

Hi,

On 2023-08-08 08:54:10 +0900, Michael Paquier wrote:
> - WaitEventExtensionShmemInit() should gain a dshash_create(), to make
> sure that the shared table is around, and we are going to have a
> reference to it in WaitEventExtensionCounterData, saved from
> dshash_get_hash_table_handle().

I'm not even sure it's worth using dshash here. Why don't we just create a
decently sized dynahash (say 128 enties) in shared memory? We overallocate
shared memory by enough that there's a lot of headroom for further entries, in
the rare cases they're needed.

> We are going to need a fixed size for these custom strings, but perhaps a
> hard limit of 256 characters for each entry of the hash table is more than
> enough for most users?

I'd just use NAMEDATALEN.

- Andres