Marc Cousin <mcousin@sigma.fr> writes:
> Nevertheless, shouldn't the third estimate be smaller or equal to the sum of the two others ?
The planner's estimation for subplan conditions is pretty primitive
compared to joinable conditions. When you add the OR, it's no longer
possible to treat the IN like a join, and everything gets an order of
magnitude dumber :-(
It might be worth trying this as a UNION of the two simple queries.
regards, tom lane