优化 BETWEEN 日期语句 [英] Optimize BETWEEN date statement

问题描述

我需要帮助优化使用 BETWEEN 子句和 timestamp 字段的 PostgreSQL 查询.

I need help in optimize a PostgreSQL query which uses the BETWEEN clause with a timestamp field.

我有两张桌子:

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

包含大约 3394 行

containing about 3394 rows

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

包含大约 4000000 行

containing about 4000000 rows

在主键 id_one 和 id_two、FK id_one 和 cut_time 上都有 btree 索引.

There are btree indexes on both PKs id_one and id_two, on the FK id_one and cut_time.

我想执行如下查询:

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';

此查询在大约 7 秒内检索了大约 1.700.000 行.

This query retrieves about 1.700.000 rows in about 7 seconds.

下面是explain analysis报告:

Below the explain analyze report is reported:

"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"

时间戳列上的索引未使用.如何优化这个查询?

The index on the timestamp column isn't used. How to optimize this query?

推荐答案

查询在不到一秒的时间内执行.其他 6 秒以上用于服务器和客户端之间的流量.

The query executes in less than one second. The other 6+ seconds are spent on traffic between server and client.

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