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为了运行查询，

SELECT count(*) FROM reservations WHERE 
(((json #>> '{details, attributes, checkIn}')::timestamptz at time zone (json #>> '{details, attributes, destinationTimeZone}'))) >= '2019-01-17' AND (((json #>> '{details, attributes, checkIn}')::timestamptz at time zone (json #>> '{details, attributes, destinationTimeZone}'))) < '2020-04-01';

我创建了功能索引：

CREATE FUNCTION text2tstz(text) RETURNS timestamp with time zone
   LANGUAGE sql IMMUTABLE AS
$$SELECT CASE WHEN $1 ~ '^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z?$'
            THEN CAST($1 AS timestamp with time zone)
       END$$;


 CREATE INDEX CONCURRENTLY checkIn_index ON reservations 
((text2tstz(json ->> '{details,attributes,checkIn}')at time zone (json ->> '{details, attributes, destinationTimeZone}')));

索引已成功创建，但是当我进行 EXPLAIN ANALYZE 时，我没有发现我的索引正在被使用，任何人都可以帮助我解决我的错误吗？

explain analyze SELECT count(*) FROM reservations WHERE 
((text2tstz(json #>> '{details, attributes, checkIn}') at time zone (json #>> '{details, attributes, destinationTimeZone}'))) >= '2019-01-17' AND ((text2tstz(json #>> '{details, attributes, checkIn}') at time zone (json #>> '{details, attributes, destinationTimeZone}'))) < '2020-04-01';

解释分析结果

Aggregate  (cost=120515.80..120515.81 rows=1 width=0) (actual time=13794.176..13794.176 rows=1 loops=1)
  ->  Seq Scan on reservations  (cost=0.00..120510.32 rows=2193 width=0) (actual time=9479.960..13792.877 rows=2973 loops=1)
        Filter: ((timezone((json #>> '{details,attributes,destinationTimeZone}'::text[]), ((json #>> '{details,attributes,checkIn}'::text[]))::timestamp with time zone) >= '2019-01-17 00:00:00'::timestamp without time zone) AND (timezone((json #>> '{details,attributes,destinationTimeZone}'::text[]), ((json #>> '{details,attributes,checkIn}'::text[]))::timestamp with time zone) < '2020-04-01 00:00:00'::timestamp without time zone))
        Rows Removed by Filter: 435536
Planning time: 0.246 ms
Execution time: 13794.257 ms

我正在使用 Postgresql 9.4.8

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1 回答 1

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你应该像这样定义你的不可变函数：

CREATE FUNCTION get_checkin(jsonb) RETURNS timestamp with time zone
   LANGUAGE sql IMMUTABLE AS
$$SELECT ($1 #>> '{details, attributes, checkIn}')::timestamptz)
AT TIME ZONE
($1 #>> '{details, attributes, destinationTimeZone}')$$;

然后您可以在索引中使用该函数：

CREATE INDEX ON reservations (get_checkin(json));

不要忘记收集统计数据：

ANALYZE reservations;

然后像这样查询：

SELECT count(*)
FROM reservations
WHERE get_checkin(json) >= '2019-01-17'
  AND get_checkin(json) < '2020-04-01';
于 2020-03-23T14:26:00.180 回答