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使用Postgres 9.6。如何有效地计算嵌套在Postgres中的JSONB数组的统计数据?
我有这个工作,但怀疑有一个更有效的方法。在MyEventLength
阵列上计算AVG,SUM等的最佳方法是什么?
DROP TABLE IF EXISTS activity;
DROP SEQUENCE IF EXISTS activity_id_seq;
CREATE SEQUENCE activity_id_seq;
CREATE TABLE activity (
id INT CHECK (id > 0) NOT NULL DEFAULT NEXTVAL ('activity_id_seq'),
user_id INT,
events JSONB
);
INSERT INTO activity (user_id,events) VALUES
(1, '{"MyEvent":{"MyEventLength":[450,790,1300,5400],"MyEventValue":[334,120,120,940]}}'),
(1, '{"MyEvent":{"MyEventLength":[12],"MyEventValue":[4]}}'),
(2, '{"MyEvent":{"MyEventLength":[450,790,1300,5400],"MyEventValue":[334,120,120,940]}}'),
(1, '{"MyEvent":{"MyEventLength":[1000,2000],"MyEventValue":[450,550]}}');
到目前为止,这是我可以找出计算的平均水平MyEventLength
阵列user_id
1的最佳方式:
SELECT avg(recs::text::numeric) FROM (
SELECT jsonb_array_elements(a.event_length) as recs FROM (
SELECT events->'MyEvent'->'MyEventLength' as event_length from activity
WHERE user_id = 1
)a
) b;
或者这种变化:
SELECT avg(recs) FROM (
SELECT jsonb_array_elements_text(a.event_length)::numeric as recs FROM (
SELECT events->'MyEvent'->'MyEventLength' as event_length from activity
WHERE user_id = 1
)a
) b;
是有没有更好的方法来做到这一点,不需要那么多的子选择?
太棒了,谢谢! – Clay