| 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: | 22795.1182874721@sss.pgh.pa.us |
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| 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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