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

[Ruslan Zakirov]

First time I see something like that. May be it's better to ask on
mysql lists. And sure you should keep digging into a reason. My
practice shows that there is no such thing as "suddenly" in IT. There
is always some change that turn world up side down.

optimize/analyze on InnoDB don't do the same job as on myisam tables,
it's documented in mysql's docs. You can find way to rebuild indexes
on a table and as the last resort use full re-load.

On Wed, Feb 18, 2009 at 2:32 AM, Tim Cutts <tjrc at sanger.ac.uk> wrote:
>
> On 17 Feb 2009, at 10:52 pm, Jesse Vincent wrote:
>
>>> OK, OPTIMIZE TABLE done, but performance on SELECT COUNT(id) FROM
>>> Attachments is still terrible:
>>>
>>> This does sort of smell like an optimiser bug - it says it's using
>>> indices, but the level of I/O being done by the machine suggests it's
>>> actually performing a full table scan.
>>
>> Indeed. Before you dig deeply into what's going on with this version
>> of
>> mysql, coming up to a current 5.0.x probably makes sense.
>
> OK, I've just moved up to 5.0.51a, as supplied in etch-backports, and
> the problem persists.  An ANALYZE TABLE on the Attachments table has
> helped a bit with the ludicrous statistics from EXPLAIN, but they're
> now just very silly rather than ludicrous:
>
> mysql> explain select count(id) from Attachments;
> +----+-------------+-------------+-------+---------------+---------
> +---------+------+---------+-------------+
> | id | select_type | table       | type  | possible_keys | key     |
> key_len | ref  | rows    | Extra       |
> +----+-------------+-------------+-------+---------------+---------
> +---------+------+---------+-------------+
> |  1 | SIMPLE      | Attachments | index | NULL          | PRIMARY |
> 4       | NULL | 2324446 | Using index |
> +----+-------------+-------------+-------+---------------+---------
> +---------+------+---------+-------------+
>
> A reload might be the way forward here.
>
> There is a part of me wondering what suddenly broke this today.  I'm
> currently searching the table for suspiciously large looking
> attachments.
>
> Tim



-- 
Best regards, Ruslan.