"Joost Kraaijeveld" <J(dot)Kraaijeveld(at)Askesis(dot)nl> writes:
> Why the difference and can I influence the result so that the first
> query plan (which is the fastest) is actually used in both cases (I
> would expect that the limit would be done after the sort?)?
It likes the second plan because 6694025.41/353 < 41812.78. It would
probably be right, too, if the number of matching rows were indeed 353,
but it seems there are only 7. Try increasing your statistics target
and re-analyzing.
regards, tom lane