1. A method for evaluating reporting window functions, the method comprising: receiving a database statement that specifies evaluating a set of reporting window functions against a set of rows, wherein each row in the set of rows has values for a plurality of columns; wherein each reporting window function in the set of reporting window functions is specified with a respective sequence of partition-by keys in a set of sequences of partition-by keys; generating a computation-pushdown execution plan for the database statement, wherein the computation-pushdown execution plan includes a plurality of producer operators and a plurality of consolidation operators, wherein each of the plurality of producer operators produces in runtime a respective subset of rows in the set of rows, wherein each of the plurality of producer operators computes a respective partial aggregation for each reporting window function in the set of reporting window functions based on the respective subset of rows in the set of rows, and wherein each of the plurality of producer operators broadcasts the respective partial aggregation for each reporting window function in the set of reporting window functions to the plurality of consolidation operators; wherein each consolidation operator of the plurality of consolidation operators evaluates each reporting window functions in the set of reporting window functions by fully aggregating all partial aggregations broadcasted from the plurality of the producer operators; wherein the method is performed by one or more computing devices.