1. A method implemented at least in part by a computer, the method comprising: for a plurality of database table partitions of a partitioned database table partitioned according to one or more partition columns of the partitioned database table, assigning the database table partitions to respective different nodes for a window calculation specified by a window operator comprising a plurality of specified PARTITION BY partition columns that are a superset of the partition columns of the partitioned database table, wherein the superset comprises one or more PARTITION BY partition columns that are not partition columns of the partitioned database table; via the database table partitions, calculating window function sub-results locally at the different nodes, wherein further partitioning to fulfill the window operator PARTITION BY partition columns that are not partition columns of the partitioned database table is performed locally in parallel across the different nodes; and combining the local window function sub-results into an overall window function result of the window operator.