1. A computer-implemented method of improving performance of schema matching, comprising: storing, by a computer system, a matching topology that maps a first data structure to a second data structure; identifying, by the computer system, a first portion of the matching topology that is a candidate for improvement as determined according to an incidence graph, wherein the incidence graph comprises a plurality of nodes, a plurality of edges between the plurality of nodes, a plurality of average runtimes associated with the plurality of nodes, and a plurality of speedup values associated with the plurality of edges; and rewriting, by the computer system, the first portion of the matching topology with a second portion according to the incidence graph, wherein the plurality of nodes includes a selected node and remaining nodes, wherein the selected node and the remaining nodes respectively have a selected average runtime and remaining average runtimes, wherein remaining edges are from the selected node to the remaining nodes, wherein identifying the first portion comprises: identifying the first portion based on a cost computed according to a selected average runtime of the selected node plus a sum of the remaining average runtimes multiplied by the speedup values associated with the remaining edges.