Re: Key/table cache size?

[Michael T. Babcock]

Dan Nelson wrote:

Yes, with only 24 values, MySQL will probably never use that index for
paring down records in a regular SELECT. But for your count() case it
should.

According to the EXPLAIN output, it does; but its still horrifically slow.

mysql> explain SELECT count(DISTINCT(sig_class_id)) FROM acid_event;
+------------+-------+---------------+--------------+---------+------+--------+-------------+
| table | type | possible_keys | key | key_len | ref | rows | Extra |
+------------+-------+---------------+--------------+---------+------+--------+-------------+
| acid_event | index | NULL | sig_class_id | 5 | NULL | 377222 | Using index |
+------------+-------+---------------+--------------+---------+------+--------+-------------+

Mind you, it doesn't pare it down much ...

--
Michael T. Babcock
C.T.O., FibreSpeed Ltd.
http://www.fibrespeed.net/~mbabcock



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