Question

我有一个看起来像这样的表

usr_id  query_ts
12345   2019/05/13 02:06
123444  2019/05/15 04:06
123444  2019/05/16 05:06
12345   2019/05/16 02:06
12345   2019/05/15 02:06

它包含用户ID和用户运行查询的时间。该表中的每个条目都代表该ID在给定的时间戳记下运行1个查询。

我正在尝试制作这个：

usr_id  day_1   day_2   …   day_30
12345   31       13           15
123444  23       41           14

我想显示每个ID在最近30天内每天运行的查询数量，如果当天没有运行查询，它将为0。

这是我提出的查询的一部分，

SELECT
t1.usr_id,
case when t1.count_day_1 is null then 0 else t1.count_day_1 end as day_1,
case when t2.count_day_2 is null then 0 else t2.count_day_2 end as day_2
FROM

(SELECT usr_id, DAY(from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "yyyy-MM-dd")) as day_1,
        COUNT( DAY(from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "yyyy-MM-dd"))) as count_day_1
        FROM db.table
        WHERE
            DAY(from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "yyyy-MM-dd")) = 1
        AND
            from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "yyyy-MM-dd")
                BETWEEN date_sub(from_unixtime(unix_timestamp()), 30)
                AND from_unixtime(unix_timestamp())
        GROUP BY usr_id, day_1) t1

LEFT JOIN
(SELECT usr_id, DAY(from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "yyyy-MM-dd")) as day_2,
        COUNT( DAY(from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "yyyy-MM-dd"))) as count_day_2
        FROM db.table
        WHERE
            DAY(from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "yyyy-MM-dd")) = 2
        AND
            from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "yyyy-MM-dd")
                BETWEEN date_sub(from_unixtime(unix_timestamp()), 30)
                AND from_unixtime(unix_timestamp())
        GROUP BY usr_id, day_2) t2
ON (t1.usr_id = t2.usr_id)
ORDER BY t1.usr_id;

这很好用，它显示前2天每天运行的查询数，并将NULL替换为0。

问题是要使它在所有30天内都能正常工作，我必须使用30个LEFT JOIN，这会在群集上拉出约400GB以上的内存。

有更简单的方法吗？

Answer 1

尝试在不进行连接的情况下执行此操作，并在WHERE中使用current_date或current_timestamp常量，而不是unix_timestamp（），此函数不是确定性的，其值在查询执行范围内也不固定，因此可以防止适当的查询优化-从2.0开始，建议使用CURRENT_TIMESTAMP常量：

select usr_id,
nvl(count(case when from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "dd") = 1 then 1 end),0) as day_1,
nvl(count(case when from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "dd") = 2 then 1 end),0) as day_2
...
from db.table
        WHERE
            from_unixtime(unix_timestamp(query_ts ,"yyyy/MM/dd"), "yyyy-MM-dd")
                BETWEEN date_sub(current_date, 30) AND current_date)
group by usr_id

从分组查询中删除联接操作

1 个答案: