Re: Support to define custom wait events for extensions

Hi,

Thanks for your comments to v1 patch.

I made v2 patch. Main changes are
* change to NAMEDATALEN
* change to use dynahash from dshash
* remove worker_spi_init()
* create second hash table to find a event id from a name to
   identify uniquness. It enable extensions which don't use share
   memory for their use to define custom wait events because
   WaitEventExtensionNew() will not allocate duplicate wait events.
* create PoC patch to show that extensions, which don't use shared
   memory for their use, can define custom wait events.
  (v2-0002-poc-custom-wait-event-for-dblink.patch)

I'm worrying about
* Is 512(wee_hash_max_size) the maximum number of the custom wait
   events sufficient?
* Is there any way to not force extensions that don't use shared
   memory for their use like dblink to acquire AddinShmemInitLock?;

Regards,
-- 
Masahiro Ikeda
NTT DATA CORPORATION