RE: speeding up planning with partitions

Amit-san,

On Wed, Mar 20, 2019 at 9:07 AM, Amit Langote wrote:
> On 2019/03/20 17:36, Imai, Yoshikazu wrote:
> > On Wed, Mar 20, 2019 at 8:21 AM, Amit Langote wrote:
> >> On 2019/03/20 12:15, Imai, Yoshikazu wrote:
> >>> [select1024.sql]
> >>> \set a random (1, 1024)
> >>> select * from rt where a = :a;
> >>>
> >>> [pgbench]
> >>> pgbench -n -f select1024.sql -T 60
> >>
> >> Thank you.
> >>
> >> Could you please try with running pgbench for a bit longer than 60
> seconds?
> >
> > I run pgbench for 180 seconds but there are still difference.
> 
> Thank you very much.
> 
> > 1024: 7,004 TPS
> > 8192: 5,859 TPS
> >
> >
> > I also tested for another number of partitions by running pgbench for
> 60 seconds.
> >
> > num of part    TPS
> > -----------  -----
> > 128          7,579
> > 256          7,528
> > 512          7,512
> > 1024         7,257 (7274, 7246, 7252)
> > 2048         6,718 (6627, 6780, 6747)
> > 4096         6,472 (6434, 6565, 6416) (quoted from above (3)'s results)
> > 8192         6,008 (6018, 5999, 6007)
> >
> >
> > I checked whether there are the process which go through the number
> of partitions, but I couldn't find. I'm really wondering why this
> degradation happens.
> 
> Indeed, it's quite puzzling why.  Will look into this.

I don't know whether it is useful, but I noticed the usage of get_tabstat_entry increased when many partitions are scanned.

--
Yoshikazu Imai