我需要优化使用该BETWEEN子句和timestamp字段的PostgreSQL查询的帮助。

我有2张桌子：

ONE(int id_one(PK), datetime cut_time, int f1 . . .)

包含约3394行

TWO(int id_two(PK), int id_one(FK), int f2 . . .)

包含约4000000行

在PKid_one和id_twoFKid_one和上都有btree索引cut_time。

我想执行类似的查询：

select o.id_one, Date(o.cut_time), o.f1, t.f2 
from one o
inner join two t ON (o.id_one = t.id_one)
where o.cut_time between '2013-01-01' and '2013-01-31';

该查询在大约7秒钟内检索到大约1.700.000行。

解释分析报告下报告：

"Merge Join  (cost=20000000003.53..20000197562.38 rows=1680916 width=24) (actual time=0.017..741.718 rows=1692345 loops=1)"
"  Merge Cond: (c.coilid = hf.coilid)"
"  ->  Index Scan using pk_coils on coils c  (cost=10000000000.00..10000000382.13 rows=1420 width=16) (actual time=0.008..4.539 rows=1404 loops=1)"
"        Filter: ((cut_time >= '2013-01-01 00:00:00'::timestamp without time zone) AND (cut_time <= '2013-01-31 00:00:00'::timestamp without time zone))"
"        Rows Removed by Filter: 1990"
"  ->  Index Scan using idx_fk_lf_data on hf_data hf  (cost=10000000000.00..10000166145.90 rows=4017625 width=16) (actual time=0.003..392.535 rows=1963386 loops=1)"
"Total runtime: 768.473 ms"

未使用时间戳列上的索引。如何优化此查询？