Re: "Constraint exclusion" is not general enough

"Florian G. Pflug" <fgp@phlo.org> writes:
> Tom Lane wrote:
>> But you don't have any cost numbers until after you've done the plan.

> Couldn't this work similar to geqo_effort? The planner could
> try planning the query using only cheap algorithmns, and if
> the cost exceeds a certain value, it'd restart, and use
> more sophisticated methods.

AFAICS this would be a net loss on average.  Most of the time, the
constraint exclusion code doesn't win, and so throwing away all your
planning work to try it is going to be a loser most of the time.
        regards, tom lane