RE: speeding up planning with partitions

Hi Amit-san.

On Fri, Feb 22, 2019 at 5:55 PM, Amit Langote wrote:
>
> Please find attached updated patches. I've made a few updates in last
> couple of hours such as improving comments, fixing a few thinkos in
> inheritance_planner changes, etc.

Thanks for the patch.

While doing code review of v24-0001, I found the performance degradation case.

[creating tables]
drop table 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, 3) x;
\gexec
\o

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

[update_pt_with_joining_another_pt.sql]
update rt set c = jrt.c + 100 from jrt where rt.b = jrt.b;

[pgbench]
pgbench -n -f update_pt_with_joining_another_pt_for_ptkey.sql -T 60 postgres

[results]
(part_num_rt, part_num_jrt) master patched(0001)
--------------------------- ------ -------------
(3, 1024) 8.06 5.89
(3, 2048) 1.52 0.87
(6, 1024) 4.11 1.77

With HEAD, we add target inheritance and source inheritance to parse->rtable in inheritance_planner and copy and adjust it for child tables at beginning of each planning of child tables.

With the 0001 patch, we add target inheritance to parse->rtable in inheritance_planner and add source inheritance to parse->rtable in make_one_rel(under grouping_planner()) during each planning of child tables.
Adding source inheritance to parse->rtable may be the same process between each planning of child tables and it might be useless. OTOH, from the POV of making inheritance-expansion-at-bottom better, expanding source inheritance in make_one_rel seems correct design to me.

How should we do that...?

--
Yoshikazu Imai