Alvaro Herrera wrote:
> There was no discussion whatsoever of the "prefetch" patch in this
> thread; and as far as I can see, nobody even mentioned such an idea in
> the thread. This prefetch patch appeared out of the blue and there was
> no discussion about it that I can see. Now I was about to push it after
> some minor tweaks, and went to search where was its justification, only
> to see that there was none. Did anybody run tests with this patch?
>
> I attach it now one more time. My version is based on the latest
> Claudio posted at
> https://postgr.es/m/CAGTBQpa464RugxYwxLTtDi=Syv9GnGFcJK8uZb2fR6NDDqULaw@mail.gmail.com
> I don't know if there are differences to the version first posted.
> I only changed the magic number 32 to a #define, and added a
> CHECK_FOR_INTERRUPTS in the prefetching loop.
Ah, I found the justification here:
https://www.postgresql.org/message-id/flat/CAGTBQpa464RugxYwxLTtDi%3DSyv9GnGFcJK8uZb2fR6NDDqULaw%40mail.gmail.com#CAGTBQpbayY-t5-ySW19yQs1dBqvV6dm8dmdpTv_FWXmDC0A0cQ%40mail.gmail.com
apparently the truncate scan is 4x-6x faster with this prefetching.
Nice!
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
