From: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
---|---|
To: | Andrei Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru> |
Cc: | jian he <jian(dot)universality(at)gmail(dot)com>, Alena Rybakina <a(dot)rybakina(at)postgrespro(dot)ru>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org, Peter Geoghegan <pg(at)bowt(dot)ie>, "Finnerty, Jim" <jfinnert(at)amazon(dot)com>, Marcos Pegoraro <marcos(at)f10(dot)com(dot)br>, teodor(at)sigaev(dot)ru, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Peter Eisentraut <peter(at)eisentraut(dot)org>, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> |
Subject: | Re: POC, WIP: OR-clause support for indexes |
Date: | 2024-03-07 14:51:43 |
Message-ID: | CAPpHfdtACtU_XbuNf9mgDBsTH1cN=i+uASXKBX_rvQk6zQ3MdQ@mail.gmail.com |
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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
Attachment | Content-Type | Size |
---|---|---|
v20-0002-Teach-generate_bitmap_or_paths-to-build-BitmapOr.patch | application/octet-stream | 34.0 KB |
v20-0001-Transform-OR-clauses-to-ANY-expression.patch | application/octet-stream | 56.1 KB |
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