Re: Speed up COPY TO text/CSV parsing using SIMD

On Tue, Mar 31, 2026 at 6:30 PM Nathan Bossart <nathandbossart(at)gmail(dot)com>
wrote:

> On Fri, Mar 27, 2026 at 07:48:38PM +0100, KAZAR Ayoub wrote:
> > I added a prescan loop inside the simd helpers trying to catch special
> > chars in sizeof(Vector8) characters, i measured how good is this at
> > reducing the overhead of starting simd and exiting at first vector:
> > the scalar loop is better than SIMD for one vector if it finds a special
> > character before 6th character, worst case is not a clean vector, where
> the
> > scalar loop needs 20 more cycles compared to SIMD.
> > This helps mitigate the case of JSON(B) in CSV format, this is why I only
> > added this for CSV case only.
>
> Interesting.
>
> > In a benchmark with 10M early SIMD exit like the JSONB case, the previous
> > 3% regression is gone.
>
> While these are nice results, I think it's best that we target v20 for this
> patch so that we have more time to benchmark and explore edge cases.
>
Thanks for the review.
Fair enough, I'll try many more cases in the upcoming weeks to make sure
we're not missing anything.

>
> --
> nathan

Regards,
Ayoub