相关疑难解决方法(0)

我想创建一个Multicolumn表达式索引,但是当我创建索引时,会输出以下消息:

--detail message 
wapgrowth=> create index CONCURRENTLY idx_test on  tmp_table using btree (skyid, to_char(create_time, 'YYYY-MM-DD'), actiontype );
ERROR:  functions in index expression must be marked IMMUTABLE


--table ddl
wapgrowth=> \d tmp_table
               Table "wapgrowth.tmp_table"
   Column    |            Type             |   Modifiers   
-------------+-----------------------------+---------------
 id          | integer                     | not null
 actiontype  | character varying(20)       | 
 apptype     | character varying(20)       | 
 score       | integer                     | 
 create_time | timestamp without time zone | default now()
 skyid       | integer                     | 
Indexes:

我正在创建一个汇总表,汇总给定日期内的所有事件.

INSERT INTO graph_6(
  day,
  event_type,
  (SELECT COUNT(*) FROM event e 
                  WHERE event_type = e.event_type 
                  AND creation_time::DATE = sq.day)
FROM event_type
CROSS JOIN
    (SELECT generate_series(
                (SELECT '2014-01-01'::DATE),
                (SELECT '2014-01-02'::DATE),
                '1 day') as day) sq;

该creation_time列已编入索引:

CREATE INDEX event_creation_time_date_idx ON event USING BTREE(creation_time);

但是,即使仅使用少量事件(2014年1月1日至2日)查询两天的数据,查询也会运行很长时间.

在EXPLAIN上查询是相当严峻-它运行一个顺序扫描的event表,而不是利用指数都:

->  Seq Scan on event e_1  (cost=0.00..12557.39 rows=531 width=38)
Filter: ... AND ((creation_time)::date = (generate_series(($12)::timestamp with time zone, ($13)::timestamp with time zone, '1 day'::interval))))

我认为这是因为我们比较了一个铸造值 - creation_time::DATE而不是creation_time.我试过索引转换: …

我有一个超过450万行的表,我的SELECT查询对我的需求来说太慢了.

该表创建于:

CREATE TABLE all_legs (
                carrier TEXT,
                dep_hub TEXT,
                arr_hub TEXT,
                dep_dt TIMESTAMP WITH TIME ZONE,
                arr_dt TIMESTAMP WITH TIME ZONE,
                price_ct INTEGER,
                ... 5 more cols ...,
                PRIMARY KEY (carrier, dep_hub, arr_hub, dep_dt, arr_dt, ...3 other cols...)
                )

当我想要SELECT特定日期的所有行时,查询太慢; 需要12秒到20秒.我的目标是最多需要1秒.我希望查询返回表中包含的行的0.1%和1%之间.

查询非常简单:

SELECT * FROM all_legs WHERE dep_dt::date = '2017-08-15' ORDER BY price_ct ASC

EXPLAIN ANALYZE 收益:

Sort  (cost=197154.69..197212.14 rows=22982 width=696) (actual time=14857.300..14890.565 rows=31074 loops=1)
  Sort Key: price_ct
  Sort Method: external merge  Disk: 5256kB
  -> …