Patent ID: 6411951
Filing Date: 2002-06-25
Classification: G06F,Y10S

Abstract:
A computerized method for evaluating a database query having at least one expression containing a subquery comprising:examining each expression in the query to determine if the expression contains a subquery; if the expression contains a subquery, classifying the expression according to a type; and extending the expression by creating an operator tree structure having a special relational operator as a root, a relation referenced by the subquery as an outer input, and an item representing the subquery as an inner input, wherein properties of the special relational operator are determined by the type of expression; creating a sensitive operator list based on a set of correlated parameters for the operator tree; producing output to create a re-computed set based on the sensitive operator list; and reusing previous data when at least one of the set of correlated parameters is unchanged during the processing of the special relational operator tree.