Robert Haas <robertmh...@gmail.com> wrote: > I think one of the problems with the planner is that all decisions > are made on the basis of cost. Honestly, it works amazingly well in > a wide variety of situations, but it can't handle things like "we > might as well materialize here, because it doesn't cost much and > there's a big upside if our estimates are off". The estimates are > the world, and you live and die by them. ["thinking out loud"] If there were some reasonable way to come up with a *range* for cost at each step, a reasonable heuristic might be to cost the plan using minimum values and maximum values, and use the root mean square of the two for comparisons to other plans. I don't know that we have a good basis to come up with ranges rather than absolute numbers, though. -Kevin
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