1. A method of processing a query in a database management system for determining a group satisfying a set predicate condition on an attribute, the method comprising: obtaining a bitmap vector of an attribute in the set predicate condition; creating a mask that identifies presence of an attribute corresponding to the obtained bitmap vector; storing the mask in a mask table; determining a group identification of each tuple; determining groups that satisfy the set predicate condition, by applying the set predicate condition to each of a plurality of entries in the mask table; determining an aggregate value of an aggregating attribute of each determined group; and obtaining multiple aggregate set predicate conditions for each group and placing the multiple aggregate set predicate conditions in a hash table.