With the proliferation of context-awareness, there is a great demand for providing the database users with suitable query results in the right place at the right time. Efficient and contextual ranking with the query results is one of the most promising way to achieve this goal. Because the users are often unwilling to show all their preferences, it is necessary to rank the query results according to their “incomplete preferences”. In this paper, we propose an optimization algorithm based on equivalence triangular condensation. The empirical studies demonstrate that there is significant improvement on time cost while it keeps quite good precision.