Hi!
>>>>> "ryc" == ryc <[EMAIL PROTECTED]> writes:
ryc> <snip>
Heikki> Well, mystery solved :). Except that why MySQL uses hours to
Heikki> sieve away the extraneous rows in the first query.
>>
>> To be able to answer the question why:
>>
>> SELECT COUNT(*) FROM table1 WHERE col1=0 and col2=0
>>
>> Is slow, I would need to get an EXPLAIN for this query.
mysql> explain select count(*) from messages where clean=0 and
ryc> parentmsgid=0;
ryc> +----------+-------+---------------+-------------+---------+------+---------
ryc> +-------------------------+
ryc> | table | type | possible_keys | key | key_len | ref | rows
ryc> | Extra |
ryc> +----------+-------+---------------+-------------+---------+------+---------
ryc> +-------------------------+
ryc> | messages | index | parentmsgid | parentmsgid | 5 | NULL | 7207120
ryc> | where used; Using index |
ryc> +----------+-------+---------------+-------------+---------+------+---------
ryc> +-------------------------+
How many rows satisfies the query? Is it about 7207120 rows ?
Heikki, could it be that InnoDB will read the original row through the
primary key even if MySQL has marked that it would be happy if InnoDB
only returned the found keys from the secondary index ?
Regards,
Monty
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