sessions table cleanup ?

[Mike McLean]

On 04/03/2012 04:35 AM, Thomas Guthmann wrote:
> Hey guys,
>
> We are running our own private koji instance. We are running 1.6 on el5.
> Lately this query takes 20mins or so to execute :
>
> SELECT host.id,name,arches,task_load,capacity FROM host
> JOIN sessions USING (user_id)
> WHERE enabled = TRUE AND ready = TRUE
> AND expired = FALSE
> AND master IS NULL
> AND update_time > NOW() - '5 minutes'::interval
>
> It looks like the 'sessions' table is the culprit. Indeed SELECTing
> 'host' is immediate whereas SELECT count(id) from 'sessions' takes 15
> seconds for only 408312 rows... looks like a vacuum problem you would
> say. You are right but my question is why do I have so many sessions
> rows ? Can 'sessions' be truncated ? I am just wondering if it's a known
> issue to not clean the sessions tables or if I need to tune my
> autovacuum to work properly :)

I run the following nightly:

DELETE FROM sessions WHERE update_time < now() - '1 day'::interval;

If you are using an old enough postgres version, you may also want to 
truncate sessions periodically. This will invalidate all login 
credentials, so I would only recommend doing so during a maintenance 
outage. This will require you to restart kojira and all kojid instances.

I'd start with just the nightly cleanup at first