1. A computer-implemented method comprising: accessing a data graph stored in memory of a database management system, wherein the data graph comprises a first plurality of vertices; receiving a query graph, wherein the query graph comprises a second plurality of vertices, and wherein the query graph causes the database management system to retrieve data from the data graph as specified in the query graph; executing in the database management system, the query graph against the data graph stored in the memory, wherein the execution generates an empty data set indicating data specified in the query graph does not exist in the data graph when the data specified in the query graph exists in the data graph; and based on the empty data set, generating a discovered component and a missing component of the query graph, wherein the discovered component includes a first vertex from the first and second plurality of vertices, and the missing component includes a second vertex from the second plurality of vertices that causes the database management system to generate the empty data set when executing the query graph.