I wrote: > However, it seems to be inapplicable for inequality operators. The plan > was improved after I added the deduce-able 'U.i = 100' in theory. Sorry, there was a miss. The correct is 'U.i < 100'. > > EXPLAIN SELECT * FROM T, U WHERE T.i = U.i AND T.i < 100; > QUERY PLAN > ----------------------------------------------------------------------------- > Merge Join (cost=0.00..340.38 rows=100 width=8) > Merge Cond: (t.i = u.i) > -> Index Scan using t_pkey on t (cost=0.00..10.00 rows=100 width=4) > Index Cond: (i < 100) > -> Index Scan using u_pkey on u (cost=0.00..3048.26 rows=100000 width=4) > > EXPLAIN SELECT * FROM T, U WHERE T.i = U.i AND T.i < 100 AND U.i < 100; > QUERY PLAN > ------------------------------------------------------------------------- > Merge Join (cost=0.00..11.32 rows=1 width=8) > Merge Cond: (t.i = u.i) > -> Index Scan using t_pkey on t (cost=0.00..10.00 rows=100 width=4) > Index Cond: (i < 100) > -> Index Scan using u_pkey on u (cost=0.00..9.94 rows=96 width=4) > Index Cond: (i < 100) Regards, --- ITAGAKI Takahiro NTT Open Source Software Center
