From: Scott Marlowe <smarlowe@g2switchworks.com>
To: Craig A. James <cjames@modgraph-usa.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Some queries starting to hang
Date: Tue, 06 Jun 2006 12:54:27 -0500
Message-ID: <1149616467.25526.213.camel@state.g2switchworks.com> (raw)
In-Reply-To: <4485C061.2080206@modgraph-usa.com>
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On Tue, 2006-06-06 at 12:50, Craig A. James wrote:
> Tom Lane wrote:
> >>The idea I just had was: why do we need EXPLAIN ANALYZE to run to
> >>completion? In severe cases like this thread, we might be able to
> >>discover the root cause by a *partial* execution of the plan, as long as
> >>it was properly instrumented. That way, the OP might have been able to
> >>discover the root cause himself...
> >
> >
> > I don't think that helps, as it just replaces one uncertainty by
> > another: how far did the EXPLAIN really get towards completion of the
> > plan? You still don't have any hard data.
>
> But at least you have some data, which is better than no data. Even knowing that the plan got stuck on a particular node of the query plan could be vital information. For a query that never finishes, you can't even find out where it's getting stuck.
>
> That's why Simon's proposal might help in some particularly difficult situations.
Hmmmmm. I wonder if it be hard to have explain analyze have a timeout
per node qualifier? Something that said if it takes more than x
milliseconds for a node to kill the explain analyze and list the up to
the nasty node that's using all the time up?
That would be extremely useful.
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To: pgsql-performance@postgresql.org
Cc: smarlowe@g2switchworks.com, cjames@modgraph-usa.com
Subject: Re: Some queries starting to hang
In-Reply-To: <1149616467.25526.213.camel@state.g2switchworks.com>
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