I need it the way it is. It's a foreign key in the actual query. Thanks! On Thu, Jul 10, 2014 at 8:31 AM, Igor Neyman <ineyman@xxxxxxxxxxxxxx> wrote: >> -----Original Message----- >> From: pgsql-general-owner@xxxxxxxxxxxxxx [mailto:pgsql-general- >> owner@xxxxxxxxxxxxxx] On Behalf Of Chris Hanks >> Sent: Thursday, July 10, 2014 5:02 AM >> To: PostgreSQL General >> Subject: [GENERAL] Joining on a view containing a UNION ALL produces a >> suboptimal plan on 9.3.4 >> >> Hi everyone - >> >> I have a slow query issue in an app I'm working on. I'm unfortunately not at >> liberty to share the query/schema details, but I've put together a very similar >> reproduction of the issue: >> >> ----- >> >> CREATE TABLE a (id integer primary key, col integer); CREATE TABLE b (id >> integer primary key, col integer); CREATE TABLE c (id integer primary key, col >> integer); CREATE TABLE d (id integer primary key, col integer); CREATE TABLE >> e (id integer primary key, col integer); >> >> INSERT INTO a (id, col) SELECT i, floor(random() * 100000) FROM >> generate_series(1, 100000, 2) i; INSERT INTO b (id, col) SELECT i, >> floor(random() * 100000) FROM generate_series(1, 100000, 2) i; INSERT INTO >> c (id, col) SELECT i, floor(random() * 100000) FROM generate_series(2, >> 100000, 2) i; INSERT INTO d (id, col) SELECT i, floor(random() * 100000) FROM >> generate_series(2, 100000, 2) i; INSERT INTO e (id, col) SELECT i, >> floor(random() * 100000) FROM generate_series(1, 100000, 1) i; >> >> ANALYZE; >> >> CREATE VIEW tables AS >> SELECT a.*, b.col AS other_col >> FROM a >> LEFT JOIN b ON a.id = b.id >> UNION ALL >> SELECT c.*, d.col AS other_col >> FROM c >> LEFT JOIN d ON c.id = d.id; >> >> EXPLAIN ANALYZE >> SELECT * >> FROM tables >> WHERE id = 89; -- Index scans, as expected. >> >> EXPLAIN ANALYZE >> SELECT * >> FROM e >> JOIN tables ON e.col = tables.id >> WHERE e.id = 568; -- Big merge joins, when simple index scans should be >> possible? >> >> ----- >> >> Would this be considered a deficiency in the optimizer? Is there a simple fix? >> >> Thanks! >> Chris >> > > Chris, > > " JOIN tables ON e.col = tables.id" - is this a typo? > > Shouldn't it be " JOIN tables ON e.id = tables.id" ? > > Or, you need it the way it is? > > Regards, > Igor Neyman > >
