在这里继续其他问题：
How to get date_part query to hit index?
执行以下查询时，它会命中我在datelocal，views，impressions，gender，agegroup字段上创建的复合索引：
SELECT date_part('hour', datelocal) AS hour
, SUM(views) FILTER (WHERE gender = 'male') AS male
, SUM(views) FILTER (WHERE gender = 'female') AS female
FROM reportimpression
WHERE datelocal >= '2019-02-01' AND datelocal < '2019-03-01'
GROUP BY 1
ORDER BY 1;
但是，我希望能够根据WHERE中的其他子句过滤此查询，例如：
SELECT date_part('hour', datelocal) AS hour
, SUM(views) FILTER (WHERE gender = 'male') AS male
, SUM(views) FILTER (WHERE gender = 'female') AS female
FROM reportimpression
WHERE datelocal >= '2019-02-01' AND datelocal < '2019-03-01'
AND network LIKE '%'
GROUP BY 1
ORDER BY 1;
第二个查询比第一个查询慢得多，尽管它应该在更少的记录上运行，此外它还没有达到我的索引。
表模式：
CREATE TABLE reportimpression (
datelocal timestamp without time zone,
devicename text,
network text,
sitecode text,
advertisername text,
mediafilename text,
gender text,
agegroup text,
views integer,
impressions integer,
dwelltime numeric
);
-- Indices -------------------------------------------------------
CREATE INDEX reportimpression_datelocal_index ON reportimpression(datelocal timestamp_ops);
CREATE INDEX reportimpression_viewership_index ON reportimpression(datelocal timestamp_ops,views int4_ops,impressions int4_ops,gender text_ops,agegroup text_ops);
CREATE INDEX reportimpression_test_index ON reportimpression(datelocal timestamp_ops,(date_part('hour'::text, datelocal)) float8_ops);
分析输出：
Finalize GroupAggregate (cost=1005368.37..1005385.70 rows=3151 width=24) (actual time=70615.636..70615.649 rows=24 loops=1)
Group Key: (date_part('hour'::text, datelocal))
-> Sort (cost=1005368.37..1005369.94 rows=3151 width=24) (actual time=70615.631..70615.634 rows=48 loops=1)
Sort Key: (date_part('hour'::text, datelocal))
Sort Method: quicksort Memory: 28kB
-> Gather (cost=1005005.62..1005331.75 rows=3151 width=24) (actual time=70615.456..70641.208 rows=48 loops=1)
Workers Planned: 1
Workers Launched: 1
-> Partial HashAggregate (cost=1004005.62..1004016.65 rows=3151 width=24) (actual time=70613.132..70613.152 rows=24 loops=2)
Group Key: date_part('hour'::text, datelocal)
-> Parallel Seq Scan on reportimpression (cost=0.00..996952.63 rows=2821195 width=17) (actual time=0.803..69876.914 rows=2429159 loops=2)
Filter: ((datelocal >= '2019-02-01 00:00:00'::timestamp without time zone) AND (datelocal < '2019-03-01 00:00:00'::timestamp without time zone) AND (network ~~ '%'::text))
Rows Removed by Filter: 6701736
Planning time: 0.195 ms
Execution time: 70641.349 ms
我是否需要创建其他索引，调整我的SELECT或其他完全？
您添加的谓词使用LIKE运算符：
AND network LIKE '%'
实际的查询计划取决于您传递的内容而不是'％'。但是，通常，普通的btree索引对此无用。您需要一个三元组索引或使用文本搜索基础结构或类似功能，具体取决于您可能要查找的模式。
看到：
您甚至可以组合多个索引策略。例：
如果那应该是：
AND network = '<input_string>'
通过各种手段，实际上使用=运算符，而不是LIKE。重要性递增的原因：