[TYPO3-english] Hunging select from fe_sessions and fe_users

[ries van Twisk]

On Mar 25, 2009, at 8:14 PM, Vahan Amirbekyan wrote:

> guys,
> I am seeing tons of queries like this one in the show process:
>
> SELECT * FROM fe_sessions,fe_users WHERE
> fe_sessions.ses_id = 'e361c16a9f' AND fe_sessions.ses_name =  
> 'fe_typo_user'
> AND fe_sessions.ses_userid = fe_users.uid
> AND (fe_sessions.ses_iplock='38.99'OR  
> fe_sessions.ses_iplock='[DISABLED]')
> AND fe_sessions.ses_hashlock=268278894 AND fe_users.disable=0 AND
> fe_users.deleted=0 AND (fe_users.starttime<=1238029426) AND
> (fe_users.endtime=0 OR fe_users.endtime>1238029426)
>
>
> I added indexes on fe_sessions.ses_userid and fe_sessions.ses_hashlock
> but it did not help much.
>
> First, why suddenly I am seeing this selects?
> What code are they from?
> And should I use MyISAM or InnoDB for these fe_sessions and fe_users  
> tables?
> I am using InnoDB.
> _______________________________________________



I don't have a direct answer, but be reminded that MySQL doesn't  
support bitmap indexes.
Adding a couple of indexes fill not gain you much, and MySQL 'might'  
even select the incorrect index
under some conditions.

Check if you have an index on fe_sessions.ses_id, this fields seems to  
be the one with the highest cardinality,
check that to be sure, I do this from the top of my head.

You might want to try to set fe_sessions to a innoDB type, I am not  
sure if a lot of deletes happen on that table,
MyISAM has a horrible track record when you need high concurency  
(lot's of read/write on the same table).

Current advice is to remove the indexes and re-investigate, check if  
you have an index on fe_sessions.ses_id.

Dmitry knows more about this stuff.. I am not really a MySQL guy.

Ries