Re: optimize lookups in snapshot [sub]xip arrays

On Wed, Aug 10, 2022 at 7:13 AM Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:
>
> On Tue, Aug 09, 2022 at 01:00:37PM -0700, Nathan Bossart wrote:
> > Your adjustments in 0002 seem reasonable to me. I think it makes sense to
> > ensure there is test coverage for pg_lfind32(), but I don't know if that
> > syscache code is the right choice. For non-USE_SSE2 builds, it might make
> > these lookups more expensive.

Yeah.

On Wed, Aug 10, 2022 at 9:25 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> I think that for non-USE_SSE2 builds, there is no additional overhead
> as all assertion-related code in pg_lfind32 depends on USE_SSE2.

Nathan is referring to RelationSupportsSysCache() and
RelationHasSysCache(). They currently use binary search and using
linear search on non-x86-64 platforms is probably slower.

[Nathan again]
> One option might be to create a small test module for pg_lfind32(). Here
> is an example.

LGTM, let's see what the buildfarm thinks of 0001.

--
John Naylor
EDB: http://www.enterprisedb.com