On Tue, Apr 19, 2016 at 10:21 AM, Mithun Cy <mithun...@enterprisedb.com> wrote: > Tests: > create table mytab(x int,x1 char(9),x2 varchar(9)); > create table mytab1(y int,y1 char(9),y2 varchar(9)); > insert into mytab values (generate_series(1,50000),'aa','aaa'); > insert into mytab1 values (generate_series(1,10000),'aa','aaa'); > insert into mytab values (generate_series(1,500000),'aa','aaa'); > insert into mytab values (generate_series(1,500000),'aa','aaa'); > analyze mytab; > analyze mytab1; > vacuum mytab; > vacuum mytab1; > > set max_parallel_degree=0; > SET > df=# SELECT count(*) FROM mytab RIGHT OUTER JOIN mytab1 > ON mytab.x = mytab1.y; > count > ------- > 30000 > (1 row) > > # set max_parallel_degree=5; > SET > df=# SELECT count(*) FROM mytab RIGHT OUTER JOIN mytab1 > ON mytab.x = mytab1.y; > count > ------- > 39089 > (1 row) > > Casue: > ====== > Normal plan > ========== > explain SELECT count(*) FROM mytab RIGHT OUTER JOIN mytab1 > ON mytab.x = mytab1.y;postgres-# > QUERY PLAN > ------------------------------------------------------------------------------ > Aggregate (cost=21682.71..21682.72 rows=1 width=8) > -> Hash Right Join (cost=289.00..21629.07 rows=21457 width=0) > Hash Cond: (mytab.x = mytab1.y) > -> Seq Scan on mytab (cost=0.00..17188.00 rows=1050000 width=4) > -> Hash (cost=164.00..164.00 rows=10000 width=4) > -> Seq Scan on mytab1 (cost=0.00..164.00 rows=10000 width=4) > ================================================================= > > Parallel plan. > ========== > explain SELECT count(*) FROM mytab RIGHT OUTER JOIN mytab1 > ON mytab.x = mytab1.y;postgres-# > QUERY PLAN > ----------------------------------------------------------------------------------------------- > Finalize Aggregate (cost=14135.88..14135.89 rows=1 width=8) > -> Gather (cost=14135.67..14135.88 rows=2 width=8) > Number of Workers: 2 > -> Partial Aggregate (cost=13135.67..13135.68 rows=1 width=8) > -> Hash Right Join (cost=289.00..13082.02 rows=21457 width=0) > Hash Cond: (mytab.x = mytab1.y) > -> Parallel Seq Scan on mytab (cost=0.00..11063.00 rows=437500 width=4) > -> Hash (cost=164.00..164.00 rows=10000 width=4) > -> Seq Scan on mytab1 (cost=0.00..164.00 rows=10000 width=4) > > > As above Right and Full join paths cannot be parallel as they can produce > false null extended rows because outer table is partial path and not > completely visible. > Adding a patch to fix same.
Committed. But I think the regression test needs more thought, so I left that out. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
