Heikki Linnakangas <heikki@enterprisedb.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