On Sat, Sep 20, 2014 at 1:33 PM, Josh Berkus <josh@agliodbs.com> wrote:
> For example, we could increase the estimated cost
> for an abort-early index scan by 10X, to reflect our weak confidence in
> its correctness.
Has any progress been made on the performance farm? The problem with
suggestions like this (which seem pretty reasonable to me) is that
we've got no way of quantifying the downside. I think this is one
example of a class of plans that are high risk. Another one off the
top of my head is nestloop joins based on assumed selectivity of
multiple stacked quals. About 90% of the time, my reflective
workaround to these types of problems is to 'disable_nestloop' which
works around 90% of the time and the result are solved with monkeying
around with 'OFFSET 0' etc. In the past, a GUC controlling planner
risk has been much discussed -- maybe it's still worth considering?
merlin