RE: speeding up planning with partitions

Amit-san,

On Wed, Mar 20, 2019 at 3:01 PM, Amit Langote wrote:
> > On Wed, Mar 20, 2019 at 2:34 AM, Amit Langote wrote:
> >> On 2019/03/20 11:21, Imai, Yoshikazu wrote:
> >>> (4)
> >>> We expect the performance does not depend on the number of
> >>> partitions
> >> after applying all patches, if possible.
> >>>
> >>> num of part    TPS
> >>> -----------  -----
> >>> 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)
> >>>
> >>> It seems the performance still depend on the number of partitions.
> >>> At
> >> the moment, I don't have any idea what cause this problem but can we
> >> improve this more?
> >>
> >> I've noticed [1] this kind of degradation when the server is built
> >> with Asserts enabled.  Did you?
> >> ...
> >> [1]
> >>
> https://www.postgresql.org/message-id/a49372b6-c044-4ac8-84ea-90ad18
> >> b1770d%40lab.ntt.co.jp
> >
> > No. I did test again from configuring without --enable-cassert but
> problem I mentioned still happens.
> 
> Hmm, OK.  Can you describe your test setup with more details?

Here the details.

[creating partitioned tables (with 1024 partitions)]
drop table if exists rt;
create table rt (a int, b int, c int) partition by range (a);
\o /dev/null
select 'create table rt' || x::text || ' partition of rt for values from (' ||
 (x)::text || ') to (' || (x+1)::text || ');' from generate_series(1, 1024) x;
\gexec
\o

[select1024.sql]
\set a random (1, 1024)
select * from rt where a = :a;

[pgbench]
pgbench -n -f select1024.sql -T 60


What I noticed so far is that it also might depends on the query. I created table with 8192 partitions and did select statements like "select * from a = :a (which ranges from 1 to 1024)" and "select * from a = :a (which ranges from 1 to 8192)", and the results of those were different.

I'll send perf to off-list.

--
Yoshikazu Imai