Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for flow analysis. In one aspect, a method includes modifying a dataflow graph, the dataflow graph including a plurality of paths connecting at least one entry point and at least one exit point, including adding components to the dataflow graph that add flow units to data records and remove flow units from data records, each flow unit identifying a segment of a path traversed by the data record. The method also includes identifying execution paths based on flow units obtained by processing a plurality of data records using the modified dataflow graph. The method also includes determining a subset of the plurality of data records, wherein a selected set of execution paths are represented by the subset.