1. A method implemented and programmed within a non-transitory computer-readable storage medium and processed by one or more processors, the processors configured to execute the method, comprising: receiving an initial assignment of first nodes to second nodes in a graph, the first nodes representing data blocks in an external distributed file system and the second nodes representing access module processors of a database management system (DBMS); constructing a residual graph with a negative cycle having an initial assignment; iterating the residual graph and with each iteration adjusting the initial assignment by any present negative cycle for the residual graph until there are no negative cycles present in the residual graph; and returning a final assignment for each of the data blocks to one of the access module processors as an assignment flow.