我有两个表,如下所示:
表_1:
-----------------------------------
| ID | customer_id | city |
-----------------------------------
| 0 | E100 | Sydney |
-----------------------------------
| 1 | E200 | Toronto |
-----------------------------------
| 2 | E300 | New York |
-----------------------------------
表_2:
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| customer_id | timestamp | receipt |
----------------------------------------------
| E200 | '2019-03-25' | 200$ |
----------------------------------------------
| E300 | '2019-03-26' | 300$ |
----------------------------------------------
| E300 | '2019-03-26' | 100$ |
----------------------------------------------
| E100 | '2019-03-27' | 50$ |
----------------------------------------------
| E100 | '2019-03-28' | 50$ |
----------------------------------------------
| E100 | '2019-03-29' | 50$ |
----------------------------------------------
我想做的是,汇总每个不同 customer_id 的所有收据。 结果表应如下所示:
----------------------------------------------
| customer_id | city | sum(receipt) |
----------------------------------------------
| E100 | Sydney | 150$ |
----------------------------------------------
| E200 | Toronto | 200$ |
----------------------------------------------
| E300 | New York | 400$ |
----------------------------------------------
为了实现这一点,我使用了以下 PostgreSQL 查询:
SELECT a.customer_id, a.city, SUM(b.receipt)
FROM public.table_1 a
INNER JOIN public.table_2 b
ON a.customer_id = b.customer_id
WHERE b.timestamp > '2019-03-25 00:00:00'
AND b.timestamp < '2019-04-01 00:00:00'
GROUP BY a.customer_id, a.city
但是,由于table_2有超过300mio行,table_1有129行, 查询花费的时间太长(我不知道究竟有多长 -> EXPLAIN ANALYZE 对此查询也没有完成)。我猜 INNER JOIN 是这里的瓶颈(如果我错了请纠正我)? 但我确实知道查询在做正确的事情,因为我已经尝试过仅过滤一天(而不是一周)。
我的问题是如何加速这个查询。我已经考虑过添加这样的索引:
CREATE INDEX table_2_index ON table_2(customer_id, timestamp)
但是这个查询也需要很长时间。
有什么建议吗?
最佳答案
尝试先聚合,再加入:
SELECT a.customer_id, a.city, b.receipt_sum
FROM public.table_1 a
JOIN (
SELECT t2.customer_id, sum(t2.receipt) as receipt_sum
FROM public.table_2 t2
WHERE t2.timestamp > '2019-03-25 00:00:00'
AND t2.timestamp < '2019-04-01 00:00:00'
GROUP BY t2.customer_id
) b ON a.customer_id = b.customer_id
关于sql - PostgreSQL:使用 join 和 group by 查询花费的时间太长,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58197142/