From: | Rafael Martinez <r(dot)m(dot)guerrero(at)usit(dot)uio(dot)no> |
---|---|
To: | Andrew Sullivan <ajs(at)crankycanuck(dot)ca>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: No control over max.num. WAL files |
Date: | 2011-05-25 13:25:50 |
Message-ID: | 4DDD035E.8040006@usit.uio.no |
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Lists: | pgsql-general |
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On 05/25/2011 02:47 PM, Andrew Sullivan wrote:
> On Wed, May 25, 2011 at 01:37:47PM +0100, Simon Riggs wrote:
>>
>> That's the way SQLServer and Oracle work, but not PostgreSQL. We can
>> clear down WAL files even during a long running transaction.
>>
>> For us, "unneeded" means prior to the second-to-last checkpoint record.
>
> Well, they're obviously not getting cleared down, so they must be
> needed ......
I wonder if full_page_writes has something to do with this.
- From the documentation:
".... If full_page_writes is set (as is the default), there is another
factor to consider. To ensure data page consistency, the first
modification of a data page after each checkpoint results in logging the
entire page content ...."
It looks like we get this 'problem' when creating a GIN index on a
tsvector column on a 4217 MB table (This takes longer than
checkpoint_timeout)
- --
Rafael Martinez Guerrero
Center for Information Technology
University of Oslo, Norway
PGP Public Key: http://folk.uio.no/rafael/
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