Re: A question on the query planner

Greg Stark <gsstark@MIT.EDU> writes:

> Huh. The following shows something strange.

Worse, with enable_hashjoin off it's even more obvious something's broken:


test=# set enable_hashjoin = off;
SET
test=# explain select * from a,b where a.x=b.x;
                            QUERY PLAN
------------------------------------------------------------------
 Merge Join  (cost=139.66..159.67 rows=1001 width=64)
   Merge Cond: ("outer"."?column2?" = "inner"."?column2?")
   ->  Sort  (cost=69.83..72.33 rows=1000 width=32)
         Sort Key: (a.x)::text
         ->  Seq Scan on a  (cost=0.00..20.00 rows=1000 width=32)
   ->  Sort  (cost=69.83..72.33 rows=1000 width=32)
         Sort Key: (b.x)::text
         ->  Seq Scan on b  (cost=0.00..20.00 rows=1000 width=32)
(8 rows)

test=# explain select * from a2,b2 where a2.x=b2.x;
                                 QUERY PLAN
-----------------------------------------------------------------------------
 Merge Join  (cost=0.00..63.04 rows=1001 width=64)
   Merge Cond: ("outer".x = "inner".x)
   ->  Index Scan using a2_pkey on a2  (cost=0.00..24.00 rows=1000 width=32)
   ->  Index Scan using b2_pkey on b2  (cost=0.00..24.00 rows=1000 width=32)
(4 rows)

--
greg