Take the attached dataset and run this query:
explain select distinct count(*) from t2 where a between 10 and 20 group by a;
|
+------+-------------+-------+-------+---------------+------+---------+------+------+---------------------------------------------------------------------+
|
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
|
+------+-------------+-------+-------+---------------+------+---------+------+------+---------------------------------------------------------------------+
|
| 1 | SIMPLE | t2 | range | a | a | 5 | NULL | 10 | Using where; Using index; Distinct; Using temporary; Using filesort |
|
+------+-------------+-------+-------+---------------+------+---------+------+------+---------------------------------------------------------------------+
|
and see an apparently non-sensical output (how can a table use "Distinct" if it
is the only table in the join?)
This is repeatable on 10.0.17, didn't check 5.5
Bug
Major