Re: Change GUC hashtable to use simplehash?

On Wed, Nov 29, 2023 at 8:31 PM John Naylor <johncnaylorls@gmail.com> wrote:
>
> Attached is a rough start with Andres's earlier ideas, to get
> something concrete out there.

While looking at the assembly out of curiosity, I found a couple bugs
in the split API that I've fixed locally.

I think the path forward is:

- performance measurements with both byte-at-a-time and
word-at-a-time, once I make sure they're fixed
- based on the above decide which one is best for guc_name_hash
- clean up hash function implementation
- test with with a new guc_name_compare (using what we learned from my
guc_name_eq) and see how well we do with keeping dynahash vs.
simplehash

Separately, for string_hash:

- run SMHasher and see about reincorporating length in the
calculation. v5 should be a clear improvement in collision behavior
over the current guc_name_hash, but we need to make sure it's at least
as good as hash_bytes, and ideally not lose anything compared to
standard fast_hash.