Bug #29244 log-queries-not-using-indexes logs all UNION SELECTs to slow query log

Description:
When using the log-queries-not-using-indexes option, all UNION SELECTs will be logged to the slow query log, even when they were fast and using indexes.

How to repeat:
my.cnf:
[mysqld]
log-slow-queries
log-queries-not-using-indexes

mysql> create table t1 (c1 int, index (c1));
Query OK, 0 rows affected (0,04 sec)

mysql> insert into t1 values (1), (2), (3), (4), (5);
Query OK, 5 rows affected (0,01 sec)
Records: 5  Duplicates: 0  Warnings: 0

mysql> explain select * from t1 where c1=2 union select * from t1 where c1=3\G
*************************** 1. row ***************************
           id: 1
  select_type: PRIMARY
        table: t1
         type: ref
possible_keys: c1
          key: c1
      key_len: 5
          ref: const
         rows: 1
        Extra: Using where; Using index
*************************** 2. row ***************************
           id: 2
  select_type: UNION
        table: t1
         type: ref
possible_keys: c1
          key: c1
      key_len: 5
          ref: const
         rows: 1
        Extra: Using where; Using index
*************************** 3. row ***************************
           id: NULL
  select_type: UNION RESULT
        table: <union1,2>
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: NULL
        Extra: 
3 rows in set (0,00 sec)

mysql> select * from t1 where c1=2 union select * from t1 where c1=3;   
+------+
| c1   |
+------+
|    2 | 
|    3 | 
+------+
2 rows in set (0,00 sec)

in slow-query.log:
# Time: 070620 17:53:17
# User@Host: root[root] @ localhost []
# Query_time: 0  Lock_time: 0  Rows_sent: 2  Rows_examined: 7
use test;
select * from t1 where c1=2 union select * from t1 where c1=3;

Suggested fix:
SELECT ... UNION statements should only be logged to the slow query log if any of the single SELECT statements would be logged.

This is severely polluting and growing our slow query log, so just wanted to add a +1 to the usefulness of this!

I have to agree with you. Logging this type of UNION queries is completely useless.

+1 the individual queries comprising the UNIONs should be considered for index usage

+1 For this issue, this have cause a lot of false positive alert if using monitoring base on slow queries status