Decomposing and pruning primary key violations from large data sets

The problem of computing the certain answer to a conjunctive query over a relational instance subject to primary key constraints is a classical hard problem in database research. On the theoretical side, we present a decomposition and pruning strategy that reduces, in polynomial time, the original problem to a collection of smaller problems of the same sort that can be solved independently. From a practical perspective, we discuss an experiment on large data sets that shows the effectiveness of the overall technique and its implementation in ASP.