A multikey hashing scheme using predicate trees

Abstract

A BSTRA CTA new method for multikey access suitable for dyna mic files is proposed that transforms multiple key values into a logical address. This method is based on a new structure, called predicate tree, that represents the function applied to several keys. A predicate tree permits to specify in a unified way various hashing schemes by allowing for diffe rent definitions of predicates. A logical address qualifies a space partition of a file according to its predicate tree. This address is seen as a sin gle key by a digital hashing method which trans forms it into a physical address. This method is used to address records in a file and to transform a retrieval qualification on a file into a set of partitions to access. Finally, a qualitative ana lysis of the behavior of the method is given which exhibits its value.

A new algorithm for computing joins with grid files

“…In [5] the records are organized using predicate trees [20]. A predicate tree defines a hash function which assigns to each tuple a partition of the corresponding file.…”

“…The superjoin algorithm can be extended to handle n-way equijoins. The hashing merhods used in [20] and [18] are quite unattractive for general database management systems, since they do not support the evaluation of range queries.…”