clickhouse 日期函式無效報錯問題處理

create

table test.user_action_log
(`event_time`
datetime,`
action
` string,
`user_id` string,
`school_id` string,
`uuid` string,
`student_id` string,
`date_key` string
)engine
= mergetree(
)partition
by date_key
primary
key user_id
order
bysettings index_granularity =
8192
;

當我們使用指定日期查詢時發現可以查詢出結果：

localhost :)

select
count(1
)from test.user_action_log where date_key =
'2020-12-04'
;select
count(1
)from test.user_action_log
where date_key =
'2020-12-04'
query id: cab1314f-
25e2-
4328
-b865-
17ede5f0c2fc
┌──count(1
)─┐│ 105338324 │
└───────────┘
1rows
inset
. elapsed: 0.002 sec.

localhost :)

select
count(1
)from test.user_action_log where date_key = addsdays(today(),
6);select
count(1
)from test.user_action_log
where date_key = addsdays(today(),
-6)query id: 8d757fd0-
6cbc-
4b95-
8b32-f87f78850db6
received exception from server (version 20.11
.3):
code: 46. db::exception: received from
10.12
.80.130:9000. db::exception: unknown function addsdays. maybe you meant: [
'adddays'
,'addyears'
]: while processing select
count(1
)from test.user_action_log where date_key = addsdays(today(),
-6).
0rows
inset
. elapsed: 0.006 sec.

經過排查我們發現建表時字段使用了string型別，而addsdays(today(), 6)生成的資料型別是date型別。這樣我們就有了兩種解決的思路。

一種是將where條件中的日期欄位強轉為date:

localhost :)

select
count(1
)from test.user_action_log where cast(date_key as
date
)= adddays(today(),
-6);
select
count(1
)from test.user_action_log
where cast(date_key,
'date'
)= adddays(today(),
-6)query id: d0fb99a6-
023f-
403a-
832b-
629ce6011b53
┌──count(1
)─┐│ 105338324 │
└───────────┘
1rows
inset
. elapsed: 0.003 sec.

另一種是將where條件中的日期欄位強轉為date:

localhost :)

select
count(1
)from test.user_action_log where date_key = cast(adddays(today(),
-6)as string)
;select
count(1
)from test.user_action_log
where date_key = cast(adddays(today(),
-6),
'string'
)query id: 20cf4d53-
07b9-
47cd-
9b66-
51356f6d625a
┌──count(1
)─┐│ 105338324 │
└───────────┘
1rows
inset
. elapsed: 0.003 sec.

我們發現引起這種問題的根本原因是建表時日期字段使用錯誤，使用為string型別而不是date型別導致，這就要求我們在建表一定要慎重使用字段型別，尤其是日期型別。

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