I has played with new hash index implementation and I tried following command:
postgres=# select * from test where id between 1 and 5; Time: 9651,033 ms postgres=# explain select * from test where id between 1 and 5; QUERY PLAN --------------------------------------------------------- Seq Scan on test (cost=0.00..141681.00 rows=1 width=4) Filter: ((id >= 1) AND (id <= 5)) (2 rows)
Hash index is created on id column. However when I use
postgres=# explain select * from test where id in (1,2,3,4,5); QUERY PLAN ------------------------------------------------------------------------- Bitmap Heap Scan on test (cost=22.24..332.53 rows=83 width=4) Recheck Cond: (id = ANY ('{1,2,3,4,5}'::integer[])) -> Bitmap Index Scan on test_idx (cost=0.00..22.22 rows=83 width=0) Index Cond: (id = ANY ('{1,2,3,4,5}'::integer[])) (4 rows)
Time: 1,352 ms
I'm not planner guru but it seems to me that BETWEEN clause could be rewritten as a IN clause for integer data types and small interval.
