Heikki Linnakangas <heikki@enterprisedb.com> writes:
> To recap, the sequence is:
> 1. COPY FROM
> 2. checkpoint
> 3. VACUUM
> Now you have buffer cache full of dirty buffers with usage_count=1,
Well, it won't be very full, because VACUUM works in a limited number of
buffers (and did even before the BufferAccessStrategy patch).
I have no doubt that there are scenarios such as you are thinking about,
but it definitely seems like a corner case that doesn't justify keeping
the all-buffers scan. That scan is costing us extra I/O in ordinary
non-corner cases, so it's not free to keep it.
regards, tom lane