On 2017-04-13 16:34:12 -0400, Robert Haas wrote: > On Thu, Mar 16, 2017 at 4:45 AM, Andres Freund <and...@anarazel.de> wrote: > > During citus development we noticed that restrictions aren't pushed down > > into lateral subqueries, even if they semantically could. For example, > > in this dumbed down example: > > > > postgres[31776][1]=# CREATE TABLE t_2(id serial primary key); > > postgres[31776][1]=# CREATE TABLE t_1(id serial primary key); > > > > Comparing: > > > > postgres[31776][1]=# EXPLAIN SELECT * FROM t_1 JOIN (SELECT * FROM t_2 > > GROUP BY id) s ON (t_1.id = s.id) WHERE t_1.id = 3; > > postgres[31776][1]=# EXPLAIN SELECT * FROM t_1, LATERAL (SELECT * FROM t_2 > > WHERE t_1.id = t_2.id GROUP BY id) s WHERE t_1.id = 3; > > Interesting. That does seem like we are missing a trick.
Yea. > Not exactly related, but I think we need to improve optimization > around CTEs, too. AFAICT, what we've got right now, almost everybody > hates. That's certainly an issue, but it's a lot harder to resolve because we've, for years, told people to intentionally use CTEs as optimization barriers :( - Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
