Hi Raghavendra, Thanks for your quick reply, I did as you suggessted and following is my output.
melaka=# set enable_mergejoin to off; SET melaka=# show enable_mergejoin; enable_mergejoin ------------------ off (1 row) Then I executed the following query melaka=# EXPLAIN select * from distributors full outer join films on distributors.did=films.did; Then the output was Merge Full Join (cost=10000000074.40..10000000093.69 rows=1159 width=286) Merge Cond: (films.did = distributors.did) -> Sort (cost=30.08..31.03 rows=380 width=184) Sort Key: films.did -> Seq Scan on films (cost=0.00..13.80 rows=380 width=184) -> Sort (cost=44.32..45.85 rows=610 width=102) Sort Key: distributors.did -> Seq Scan on distributors (cost=0.00..16.10 rows=610 width=102) (8 rows) Can you suggest why the merge join is being suggested when I have turned it off ? On Sun, Sep 18, 2011 at 3:05 PM, Raghavendra < raghavendra....@enterprisedb.com> wrote: > postgres=# set enable_hashjoin to off; > SET > postgres=# show enable_hashjoin; > enable_hashjoin > ----------------- > off > (1 row) > > Above, changes applies for the current session (its Session-Level). If you > want to do at Database-level use ALTER DATABASE and for entire Cluster-level > edit postgresql.conf and do changes as per your requirement. > > --- > Regards, > Raghavendra > EnterpriseDB Corporation > Blog: http://raghavt.blogspot.com/ > > > > On Sun, Sep 18, 2011 at 2:55 PM, Melaka Gunasekara <donmel...@gmail.com>wrote: > >> Hi all, >> >> I came across >> http://www.postgresql.org/docs/8.4/static/runtime-config-query.html which >> describes >> how to change query planner configuration paramerters. >> >> I need to know how I can change these parameters. >> For example if I need to turn off enable_hashjoin, how can I do that? >> >> Best Regards, >> Melaka >> >> > -- Best Regards, Melaka
