Re: Faster str to int conversion (was Table with large number of int columns, very slow COPY FROM)

Hi,

On 2017-12-08 13:44:37 -0800, Andres Freund wrote:
> On 2017-12-08 10:17:34 -0800, Andres Freund wrote:
> > the strtoll is libc functionality triggered by pg_atoi(), something I've
> > seen show up in numerous profiles. I think it's probably time to have
> > our own optimized version of it rather than relying on libcs.
>
> Attached is a hand-rolled version. After quickly hacking up one from
> scratch, I noticed we already kind of have one for int64 (scanint8), so
> I changed the structure of this one to be relatively similar.
>
> It's currently using the overflow logic from [1], but that's not
> fundamentally required, we could rely on fwrapv for this one too.
>
> This one improves performance of the submitted workload from 1223.950ms
> to 1020.640ms (best of three). The profile's shape changes quite
> noticeably:

FWIW, here's a rebased version of this patch. Could probably be polished
further. One might argue that we should do a bit more wide ranging
changes, to convert scanint8 and pg_atoi to be also unified. But it
might also just be worthwhile to apply without those, given the
performance benefit.

Anybody have an opinion on that?

Greetings,

Andres Freund