Silvio Matthes <silvio.matthes@xcom.de> writes:
> But in my opinion with the multicolumn index in mind the server should do
> a index scan, because there are only 7 rows with param_name='KUNDEN_NR'
> and param_value=''?!?
We do not have any cross-column statistics at the moment, so the planner
is unable to recognize the potential win here. Note the poor estimate
of the number of matching rows in your EXPLAIN result.
I think though that it might help to put param_name first in the
multicolumn index.
regards, tom lane