Re: Use simplehash.h instead of dynahash in SMgr

On Mon, 4 Oct 2021 at 20:37, Jaime Casanova
<jcasanov(at)systemguards(dot)com(dot)ec> wrote:
> Based on your comments I will mark this patch as withdrawn at midday of
> my monday unless someone objects to that.

I really think we need a hash table implementation that's faster than
dynahash and supports stable pointers to elements (simplehash does not
have stable pointers). I think withdrawing this won't help us move
towards getting that.

Thomas voiced his concerns here about having an extra hash table
implementation and then also concerns that I've coded the hash table
code to be fast to iterate over the hashed items. To be honest, I
think both Andres and Thomas must be misunderstanding the bitmap part.
I get the impression that they both think the bitmap is solely there
to make interations faster, but in reality it's primarily there as a
compact freelist and can also be used to make iterations over sparsely
populated tables fast. For the freelist we look for 0-bits, and we
look for 1-bits during iteration.

I think I'd much rather talk about the concerns here than just
withdraw this. Even if what I have today just serves as something to
aid discussion.

It would also be good to get the points Andres raised with me off-list
on this thread. I think his primary concern was that bitmaps are
slow, but I don't really think maintaining full pointers into freed
items is going to improve the performance of this.

David