Tom Lane wrote:
>
> Don Baccus <dhogaza@pacifier.com> writes:
> > While I don't doubt your analysis is correct for the case you've
> > uncovered, it doesn't explain why surrounding a bunch of selects
> > with a begin/end block greatly descreases disk activity for tables
> > that don't change.
>
> Hmm, I'm not sure why that should be, either. Anyone?
>From a recent discussion I remember that every block that is read
in is marked as dirty, regardless of weather it is modified or not.
It is not a genuine bug (as it only slows thong down instead of
getting wrong results), but still a misfeature.
It is most likely an ancient quickfix for some execution path that
failed to set the dirty mark when it should have.
---------------------
Hannu
