Re: regex cache

Josh Berkus <josh(at)agliodbs(dot)com> writes:
> Tom Lane wrote:
>> Hmm. Well, I still don't want to tie it to work_mem; how do you feel
>> about a new GUC to determine the max number of cached REs?

> Yeah. You know me, I was just trying to avoid having more GUCs.

I'm not excited about it either, but I think if we're going to make
this adjustable it does need its own knob. I can easily believe
that a large list of precompiled GUCs could be counterproductive
given a workload where you don't get much reuse, so I don't want
the list size going to the moon just because someone cranked up
work_mem for other purposes.

(I'm not real sure that that "self-organizing list" data structure
would work well beyond 1000 or so entries even if you did have
enough re-use to justify them all. Anyone want to try to do some
performance testing? In particular I think we might want to drop
the move-to-front approach in favor of move-up-one, just to avoid
O(N^2) memmove costs.)

regards, tom lane