Abstract: A join optimization method is provided for use with a data processor for optimizing the processing of a query for retrieval of data from a relational computer database. The database is organized by relations and data is retrieved by preforming join operations on the relations. The join operations are optimized by randomly selecting an initial order for the join operations, assigning optimal join methods based on the initial order, finding an optimal order based on the assigned methods and repeating a polynomial number of times. The Krishanmurthy, Boral and Zaniolo (KBZ) Algorithm is used to determine a join optimization sequence and further refinement is provided by determining costs for alternate join order sequences using alternate join methods.

Abstract: A system is described for producing a near-random hash value from a key value. In a preferred embodiment the system comprises the steps of combining each key byte in turn with a corresponding byte in a predefined table; substituting each key byte with a byte from a second table, the location of the substitute byte in the table being equal to the value of the key byte; and using a propagated exclusive-OR to produce a four-byte value, which is then manipulated and scaled to produce a hash value in the desired range.