Select doesn't use the different partitions?

[Frank Schuster]

Hello,

I have a log table with a few millionen data records.
And I have a list partitioning for timestamp (DATETIME)
/*!50100 PARTITION BY LIST (MONTH(timestamp))
(PARTITION m5 VALUES IN (5) ENGINE = MyISAM,
PARTITION m6 VALUES IN (6) ENGINE = MyISAM,
PARTITION m7 VALUES IN (7) ENGINE = MyISAM,
PARTITION m8 VALUES IN (8) ENGINE = MyISAM) */ |

But, when I do:
explain partitions select count(*) from log USE index(timestamp) where timestamp between '2009-06-01 00:00:00' and '2009-06-31 23:59:59';

I thought, that this query use only partition 6 with about 6 million records.
But explain shows all records in the database. So the query use more than one partition.
+----+-------------+--------+-------------+-------+---------------+-----------+---------+------+--------+--------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------+-------------+-------+---------------+-----------+---------+------+--------+--------------------------+
| 1 | SIMPLE | logs | m5,m6,m7,m8 | range | timestamp | timestamp | 8 | NULL | 11132772 | Using where; Using index |
+----+-------------+--------+-------------+-------+---------------+-----------+---------+------+--------+--------------------------+


What I do wrong or where is the problem?



Edited 1 time(s). Last edit at 07/28/2009 04:54AM by Frank Schuster.