Indexes Cardinality is NULL on Partitioned tables.

[Rushi Vishavadia]

Hi,

I'm doing some testing with partitioned tables and I'm having some issues with indexes. Here I have just created a test table:

-- Simple table partitioned on date.
drop table by_month;
CREATE TABLE by_month (
d DATE,
i int(4),
KEY(i)
)
PARTITION BY RANGE (TO_DAYS(d))
(
PARTITION P1 VALUES LESS THAN (to_days('2001-02-01')),
PARTITION P2 VALUES LESS THAN (to_days('2001-03-01')),
PARTITION P3 VALUES LESS THAN (to_days('2001-04-01')),
PARTITION P4 VALUES LESS THAN (MAXVALUE)
);

-- I insert a bunch of data, say 10 rows via simple inserts
insert into by_month values('2001-01-01','1314645');

mysql> show indexes from by_month;
+----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| by_month | 1 | i | 1 | i | A | NULL | NULL | NULL | YES | BTREE | |
+----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+


Why is the cardinality NULL ? If I execute a "repair table by_month" it fixes the indexes and the cardinality shows up fine.

I checked the .MYI file, and it was built fine. I've tried this on several servers and I am having the same problem. Any clues?