Re: speeding up planning with partitions

On Sun, Mar 31, 2019 at 12:11 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Amit Langote <amitlangote09(at)gmail(dot)com> writes:
> > I think the performance results did prove that degradation due to
> > those loops over part_rels becomes significant for very large
> > partition counts. Is there a better solution than the bitmapset that
> > you have in mind?
>
> Hm, I didn't see much degradation in what you posted in
> <5c83dbca-12b5-1acf-0e85-58299e464a26(at)lab(dot)ntt(dot)co(dot)jp>.

Sorry that I didn't mention the link to begin with, but I meant to
point to numbers that I reported on Monday this week.

https://www.postgresql.org/message-id/19f54c17-1619-b228-10e5-ca343be6a4e8%40lab.ntt.co.jp

You were complaining of the bitmapset being useless overhead for small
partition counts, but the numbers I get tend to suggest that any
degradation in performance is within noise range, whereas the
performance benefit from having them looks pretty significant for very
large partition counts.

> I am curious as to why there seems to be more degradation
> for hash cases, as per Yoshikazu-san's results in
> <0F97FA9ABBDBE54F91744A9B37151A512BAC60(at)g01jpexmbkw24>,
> but whatever's accounting for the difference probably
> is not that.

I suspected it may have been the lack of bitmapsets, but maybe only
Imai-san could've confirmed that by applying the live_parts patch too.

Thanks,
Amit