[rt-users] mysql 5.1 slow query in RT

[Micah Gersten]

What are your indices on?  Which columns?

Thank you,
Micah Gersten
onShore Networks
Internal Developer
http://www.onshore.com



Mike Zupan wrote:
> We moved our RT server from mysql 4.0 to 5.1 and we are having some
> slow query issues on the Attachments table not finding the correct index
>
>
> mysql> explain SELECT main.* FROM Attachments main WHERE (main.Parent
> = '308267') AND (main.ContentType = 'text/plain') ORDER BY main.id
> <http://main.id> ASC;
> +----+-------------+-------+-------+----------------------------------+---------+---------+------+---------+-------------+
> | id | select_type | table | type | possible_keys | key | key_len |
> ref | rows | Extra |
> +----+-------------+-------+-------+----------------------------------+---------+---------+------+---------+-------------+
> | 1 | SIMPLE | main | index | Attachments3,Attachments4,Parent |
> PRIMARY | 4 | NULL | 1321158 | Using where |
> +----+-------------+-------+-------+----------------------------------+---------+---------+------+---------+-------------+
> 1 row in set (0.00 sec)
>
>
> mysql> explain SELECT main.* FROM Attachments main FORCE
> INDEX(Attachments3) WHERE (main.Parent = '308267') AND
> (main.ContentType = 'text/plain') ORDER BY main.id <http://main.id> ASC;
> +----+-------------+-------+------+---------------+--------------+---------+-------+------+-----------------------------+
> | id | select_type | table | type | possible_keys | key | key_len |
> ref | rows | Extra |
> +----+-------------+-------+------+---------------+--------------+---------+-------+------+-----------------------------+
> | 1 | SIMPLE | main | ref | Attachments3 | Attachments3 | 4 | const |
> 1 | Using where; Using filesort |
> +----+-------------+-------+------+---------------+--------------+---------+-------+------+-----------------------------+
> 1 row in set (0.00 sec)
>
>
> It works if I choose to force the index.
>
> I have been trying to find where in the code this is to at least force
> the index but I have not found it.
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