Re: Change GUC hashtable to use simplehash?

Hi,

On 2023-11-17 13:44:21 -0800, Jeff Davis wrote:
> On Fri, 2023-11-17 at 13:22 -0800, Gurjeet Singh wrote:
> > This is not a comment on the patch itself, but since GUC operations
> > are not typically considered performance or space sensitive,

I don't think that's quite right - we have a lot of GUCs and they're loaded in
each connection. And there's set/reset around transactions etc. So even
without search path stuff that Jeff mentioned, it could be worth optimizing
this.

> Yeah, that's what I was thinking. simplehash is newer and has a nicer
> API, so if we like it and want to move more code over, this is one
> step. But if we are fine using both hsearch.h and simplehash.h for
> overlapping use cases indefinitely, then I'll drop this.

Right now there are use cases where simplehash isn't really usable (if stable
pointers to hash elements are needed and/or the entries are very large). I've
been wondering about providing a layer ontop of simplehash, or an option to
simplehash, providing that though. That then could perhaps also implement
runtime defined key sizes.

I think this would be a completely fair thing to port over - whether it's
worth it I don't quite know, but I'd not be against it on principle or such.

Greetings,

Andres Freund