Re: POC, WIP: OR-clause support for indexes

Hi!

On Tue, Mar 5, 2024 at 9:59 AM Andrei Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru>
wrote:
> On 5/3/2024 12:30, Andrei Lepikhov wrote:
> > On 4/3/2024 09:26, jian he wrote:
> ... and the new version of the patchset is attached.

I made some revisions for the patchset.
1) Use hash_combine() to combine hash values.
2) Upper limit the number of array elements by MAX_SAOP_ARRAY_SIZE.
3) Better save the original order of clauses by putting hash entries and
untransformable clauses to the same list. A lot of differences in
regression tests output have gone.

One important issue I found.

# create table t as (select i::int%100 i from generate_series(1,10000) i);
# analyze t;
# explain select * from t where i = 1 or i = 1;
QUERY PLAN
-----------------------------------------------------
Seq Scan on t (cost=0.00..189.00 rows=200 width=4)
Filter: (i = ANY ('{1,1}'::integer[]))
(2 rows)

# set enable_or_transformation = false;
SET
# explain select * from t where i = 1 or i = 1;
QUERY PLAN
-----------------------------------------------------
Seq Scan on t (cost=0.00..189.00 rows=100 width=4)
Filter: (i = 1)
(2 rows)

We don't make array values unique. That might make query execution
performance somewhat worse, and also makes selectivity estimation worse. I
suggest Andrei and/or Alena should implement making array values unique.

------
Regards,
Alexander Korotkov