Re: [HACKERS] path toward faster partition pruning

On 21 December 2017 at 23:38, Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> Attached updated set of patches.

Looks like the new not equals code does not properly take into account
a missing NULL partition.

create table ta (a int not null) partition by list (a);
create table ta1 partition of ta for values in(1,2);
create table ta2 partition of ta for values in(3,4);
explain select * from ta where a <> 1 and a <> 2;
ERROR: negative bitmapset member not allowed

-- Add null partition
create table ta_null partition of ta for values in(null);
explain select * from ta where a <> 1 and a <> 2; -- works now.
QUERY PLAN
-------------------------------------------------------------
Append (cost=0.00..48.25 rows=2525 width=4)
-> Seq Scan on ta2 (cost=0.00..48.25 rows=2525 width=4)
Filter: ((a <> 1) AND (a <> 2))
(3 rows)

This code appears to be at fault:

/*
* Also, exclude the "null-only" partition, because strict clauses in
* ne_clauses will not select any rows from it.
*/
if (count_partition_datums(relation, boundinfo->null_index) == 0)
excluded_parts = bms_add_member(excluded_parts,
boundinfo->null_index);

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