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From: Rafael Martinez <[email protected]>
To: Robert Haas <[email protected]>
Cc: [email protected]
Subject: Re: Information about WAL Configuration needs an update
Date: Mon, 13 Jun 2011 20:25:11 +0200
Message-ID: <1307989511.2862.810.camel@core2> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

On Mon, 2011-06-13 at 13:24 -0400, Robert Haas wrote:
> On Fri, Jun 3, 2011 at 3:42 AM, Rafael Martinez
> >
> > You can see the graph with the generation of WAL files + some extra
> > information for this test here: http://folk.uio.no/rafael/total_wal/
> >
> > What do you think? Shouldn't we update the documentation with some
> > information about this?
> 
> Perhaps, but we'd have to think of something intelligent to say about
> it first.  We can't remove the old WAL files until we successfully
> checkpoint, and so I think if checkpoints are taking a very long to
> complete or failing altogether, there's actually no upper bound.  I
> don't think we have any kind of "hard stop" where, if no log space is
> available, we just refuse to process write transactions - such a thing
> would seem to be rather dangerous.
> 

Well, a good start will be to try to identify or describe the situations
where checkpoints can take very long to complete or fail altogether.

I have the first one: Creating a large GIN index on a tsvector column. I
don't know why, maybe somebody who knows postgres internals can explain
why a creation of an index can create this situation.

regards,
-- 
Rafael Martinez Guerrero
Center for Information Technology
University of Oslo, Norway

PGP Public Key: http://folk.uio.no/rafael/



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