Re: Speeding up GIST index creation for tsvectors

On Sun, Aug 1, 2021 at 11:41 PM Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>
wrote:
>
> > FWIW, I anticipate some push back from the community because of the
fact that the optimization relies on statistical phenomena.
>
> I dug into this issue for tsvector type. Found out that it's the way
> in which the sign array elements are arranged that is causing the
pointers to
> be misaligned:
[...]
> If siglen is not a multiple of 8 (say 700), cache[j].sign will in some
> cases point to non-8-byte-aligned addresses, as you can see in the
> above code snippet.
>
> Replacing siglen by MAXALIGN64(siglen) in the above snippet gets rid
> of the misalignment. This change applied over the 0001-v3 patch gives
> additional ~15% benefit. MAXALIGN64(siglen) will cause a bit more
> space, but for not-so-small siglens, this looks worth doing. Haven't
> yet checked into types other than tsvector.

Sounds good.

> Will get back with your other review comments. I thought, meanwhile, I
> can post the above update first.

Thinking some more, my discomfort with inline functions that call a global
function doesn't make logical sense, so feel free to do it that way if you
like.

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