Heikki Linnakangas <[EMAIL PROTECTED]> writes:
> To recap, the sequence is:

> 2. checkpoint

> 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

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