1. A computer program product comprising a computer readable medium having computer program logic recorded thereon for enabling a computer system to optimize performance of a heterogeneous, distributed database system comprising a plurality of heterogeneous database management systems, wherein data associated with a client is distributed among said heterogeneous database management systems, said computer program product comprising: means for evaluating a query for data coverage by determining whether all data referenced in said query is located within a single database instance; means for evaluating said query for capability coverage by determining whether all capabilities referenced in said query can be performed by said single database instance; and means for pushing down the query to said single database instance if said data coverage and said capability coverage are satisfied.