1. A computer-readable medium storing computer-executable instructions that when executed by a computer cause the computer to perform a method, the method comprising: selecting a first engine for searching a graph for instances of a pre-specified sub-graph, where the first engine is selected as a function of graph-level information associated with one or more of, the graph, and the pre-specified sub-graph; controlling execution of a search for the pre-specified sub-graph using the first engine; and storing performance data associated with one or more of the pre-specified sub-graph and the first engine describing a performance indicator of the search.