Jeff Janes <jeff.janes@gmail.com> writes:
> One thing I wanted to play with is having newly read buffers get a
> usage count of 0 rather than 1. The problem is that there is no way
> to test it in enough different situations to convince people it would
> be a general improvement.
Hmm ... ISTM that that was discussed back when we instituted buffer
usage counts, and rejected on the grounds that a newly-read buffer could
then have negligible life expectancy. The clock sweep might be just
about to pass over it. By starting at 1, it's guaranteed to have at
least 1 sweep cycle time in which it might accumulate more hits.
In other words, we have a choice of whether a buffer's initial lifetime
is between 0 and 1 sweep times, or between 1 and 2 sweep times; and the
discrimination against an unlucky buffer position is infinite in the
first case versus at most 2X in the second case.
regards, tom lane
