Re: [HACKERS] path toward faster partition pruning

On 30 March 2018 at 18:38, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> Please find attached the updated patches.

There's a bit of a strange case with v45 around prepared statements.
I've not debugged this yet, but in case you get there first, here's
the case:

create table listp (a int, b int) partition by list (a);
create table listp_1 partition of listp for values in(1) partition by list (b);
create table listp_1_1 partition of listp_1 for values in(1);
create table listp_2 partition of listp for values in(2) partition by list (b);
create table listp_2_1 partition of listp_2 for values in(2);

explain select * from listp where b in(1,2) and 2<>b and 0<>b; -- this
one looks fine.
QUERY PLAN
----------------------------------------------------------------------------
Append (cost=0.00..49.66 rows=22 width=8)
-> Seq Scan on listp_1_1 (cost=0.00..49.55 rows=22 width=8)
Filter: ((b = ANY ('{1,2}'::integer[])) AND (2 <> b) AND (0 <> b))
(3 rows)

prepare q1 (int,int,int,int) as select * from listp where b in($1,$2)
and $3 <> b and $4 <> b;
execute q1 (1,2,3,4);
execute q1 (1,2,3,4);
execute q1 (1,2,3,4);
execute q1 (1,2,3,4);
execute q1 (1,2,3,4);
explain (analyze, costs off, summary off, timing off) execute q1 (1,2,2,0);
QUERY PLAN
--------------------------------
Result (actual rows=0 loops=1)
One-Time Filter: false
(2 rows)

My best guess is that something ate the bits out of a Bitmapset of the
matching partitions somewhere.

--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services