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Re: Load Distributed Checkpoints, take 3

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
Cc: Greg Smith <gsmith(at)gregsmith(dot)com>, Patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: Load Distributed Checkpoints, take 3
Date: 2007-06-26 16:18:41
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-patches
Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
> Tom Lane wrote:
>> This argument supposes that the bgwriter will do nothing while the COPY
>> is proceeding.

> It will clean buffers ahead of the COPY, but it won't write the buffers 
> COPY leaves behind since they have usage_count=1.

Yeah, and they don't *need* to be written until the clock sweep has
passed over them once.  I'm not impressed with the idea of writing
buffers because we might need them someday; that just costs extra
I/O due to re-dirtying in too many scenarios.

(Note that COPY per se will not trigger this behavior anyway, since it
will act in a limited number of buffers because of the recent buffer
access strategy patch.)

			regards, tom lane

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Subject: Re: Load Distributed Checkpoints, take 3
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