Thread: Out of control query

I have an inventory system based on PostgreSQL 8.3.5, JBoss, Hibernate......

I have a query builder that lets users filter data in a fairly complex way.

For some reason the search gets out of control and consumes all CPU.

I set my statement timeout to 2 minutes and this keeps the system from going down totally, but this is happening much more frequently than it used to.

I can find the problem with the individual query easily enough, but I would like a more general solution.

What seems strange to me is that one one core of my Quad core x5472 is 100%.  The others show minimal usage.

I would think that other users would get a different core and one query could not deadlock the whole system for everyone.

Do you think this is due to my Postgres or JBoss AS configuration for database connections?

Any advice will be greatly appreciated.

On Fri, 2008-12-19 at 16:20 -0600, Jason Long wrote:
> I have an inventory system based on PostgreSQL 8.3.5, JBoss,
> Hibernate......
>
> I have a query builder that lets users filter data in a fairly complex
> way.
>
> For some reason the search gets out of control and consumes all CPU.
>
> I set my statement timeout to 2 minutes and this keeps the system from
> going down totally, but this is happening much more frequently than it
> used to.
>
> I can find the problem with the individual query easily enough, but I
> would like a more general solution.
>
> What seems strange to me is that one one core of my Quad core x5472 is
> 100%.  The others show minimal usage.
>
> I would think that other users would get a different core and one
> query could not deadlock the whole system for everyone.
>
> Do you think this is due to my Postgres or JBoss AS configuration for
> database connections?
>
> Any advice will be greatly appreciated.

An explain analyze of the query would be useful.

Joshua D. Drake


--
PostgreSQL
   Consulting, Development, Support, Training
   503-667-4564 - http://www.commandprompt.com/
   The PostgreSQL Company, serving since 1997

Jason Long wrote:

> For some reason the search gets out of control and consumes all CPU.
> [snip]
> What seems strange to me is that one one core of my Quad core x5472 is
> 100%.  The others show minimal usage.

Consuming all of one CPU is quite normal if a query requires a lot of
CPU-intensive work such as some types of text processing, calculations,
etc. I have quite a few CPU-bound queries in the system I'm working
with, and they cause no problems.

> I would think that other users would get a different core and one query
> could not deadlock the whole system for everyone.

That should indeed be the case. Are your other users completely unable
to run queries, or are they just too slow? Have you tested by connecting
with `psql' and running queries by hand? Have you checked the pg_locks
table to see if there's any possible locking issue preventing the other
users from proceeding with their queries? Is your disk subsystem also
working hard during these difficult queries?

--
Craig Ringer