count(distinct col) renturn null

[yidwf]

mybatis：int getMsgDay(@param("account_uid") String account_uid);

SQL：SELECT COUNT(DISTINCT DATE_FORMAT(create_time,'%Y%m%d')) as count FROM table_name
WHERE account_uid = #{account_uid}

if there is no data, then return null, not return 0, it case an exection:
org.apache.ibatis.binding.BindingException: Mapper method 'com.*.getMsgDay attempted to return null from a method with a primitive return type (int).

[kimmking]

I will try to reproduce this issue later, maybe tomorrow.

[kimmking]

I reproduced it. It's a bug.

[kimmking]

AggregationType(MAX, MIN, SUM, COUNT, AVG) + Distinct all have this problem.
I will fix later.

[kimmking]

I will fix to show:

mysql> select avg(distinct id),name from test;
+--------------------------------+------+
| AGGREGATION_DISTINCT_DERIVED_0 | name |
+--------------------------------+------+
|                           NULL | NULL |
+--------------------------------+------+
1 row in set (0.04 sec)

mysql> select sum(distinct id),name from test;
+--------------------------------+------+
| AGGREGATION_DISTINCT_DERIVED_0 | name |
+--------------------------------+------+
|                           NULL | NULL |
+--------------------------------+------+
1 row in set (0.02 sec)

mysql> select count(distinct id),name from test;
+--------------------------------+------+
| AGGREGATION_DISTINCT_DERIVED_0 | name |
+--------------------------------+------+
|                              0 | NULL |
+--------------------------------+------+
1 row in set (0.01 sec)

mysql> select min(distinct id),name from test;
+--------------------------------+------+
| AGGREGATION_DISTINCT_DERIVED_0 | name |
+--------------------------------+------+
|                           NULL | NULL |
+--------------------------------+------+
1 row in set (0.02 sec)

mysql>
mysql> select max(distinct id),name from test;
+--------------------------------+------+
| AGGREGATION_DISTINCT_DERIVED_0 | name |
+--------------------------------+------+
|                           NULL | NULL |
+--------------------------------+------+
1 row in set (0.01 sec)


mysql> select max(distinct id) as a,name from test;
+---+------+
| a | name |
+---+------+
| NULL | NULL |
+---+------+
1 row in set (0.02 sec)

mysql> select count(distinct id) as a,name from test;
+---+------+
| a | name |
+---+------+
| 0 | NULL |
+---+------+
1 row in set (0.01 sec)

mysql> select avg(distinct id) as a,name from test;
+---+------+
| a | name |
+---+------+
| NULL | NULL |
+---+------+
1 row in set (0.01 sec)

[changchangjie]

+1

[tristaZero]

+1

Hi this issue has been fixed already. If it is convenient, you can give it a test on the master branch. Thx.

[changchangjie]

+1

Hi this issue has been fixed already. If it is convenient, you can give it a test on the master branch. Thx.

I'm using version 4.0.0-RC3. Which version should I upgrade to