[rt-users] Severe performance problems suddenly in RT 3.8.2

[Dave Holland]

Tim's just got into his car to go home, but I can provide some
answers...

On Tue, Feb 17, 2009 at 12:29:10PM -0500, Jesse Vincent wrote:
> On Tue 17.Feb'09 at 16:51:57 +0000, Tim Cutts wrote:
> > We migrated our RT server to RT 3.8.2 a week ago, and all went well  
> > until today, 
> From what version?

3.4.2

> Anything in mysql's error logs?

No, only the messages in the slow log, e.g:

# Query_time: 240  Lock_time: 0  Rows_sent: 4  Rows_examined: 27
SELECT DISTINCT main.Id AS id, main.Filename AS filename,
main.ContentType AS contenttype, main.Headers AS headers, main.Subject
AS subject, main.Parent AS parent, main.ContentEncoding AS
contentencoding, main.ContentType AS contenttype, main.TransactionId AS
transactionid, main.Created AS created FROM Attachments main JOIN
Transactions Transactions_1  ON ( Transactions_1.id = main.TransactionId
) JOIN Tickets Tickets_2 ON ( Tickets_2.id = Transactions_1.ObjectId )
WHERE (Tickets_2.EffectiveId = '97814') AND (Transactions_1.ObjectType =
'RT::Ticket')  ORDER BY main.id ASC;

and

# Query_time: 275  Lock_time: 0  Rows_sent: 1  Rows_examined: 806085
select count(id) from Attachments;

> What does EXPLAIN SELECT COUNT(id) FROM Attachments say?

| id | select_type | table       | type  | possible_keys | key     | key_len | ref  | rows    | Extra       |
+----+-------------+-------------+-------+---------------+---------+---------+------+---------+-------------+
|  1 | SIMPLE      | Attachments | index | NULL          | PRIMARY | 4       | NULL | 2698295 | Using index | 

> MySQL versions > 4.1 and < 5.0.45 are known to have a crippling query
> optimizer bug that WILL hurt you on RT, but I'm not sure this is that.

Any pointers, please? I couldn't see anything in the RT wiki, sorry.

This is on Debian Etch so I expect we can upgrade to 5.0.51 from
backports quite easily if need be.

thanks,
Dave
-- 
** Dave Holland ** Systems Support -- Infrastructure Management **
** 01223 496923 ** The Sanger Institute, Hinxton, Cambridge, UK **
"An infinite number of mathematicians walk into a bar..."


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