Description:
The design of a microprogrammable microprocessor-based keyword transformation unit for a database computer(DBC) is described. The DBC, a specialized back-end computer capable of managing 10 9 - 10 10 bytes of data, consists of two loops of memories and processors, the structure loop and the data loop, connected through a database command and control processor (DBCCP). The structure loop is used to retrieve and update the large amount (10 7 - 10 9 bytes) of structural information about the database from a structure memory (SM) at a rate commensurate with the database operations performed on the mass memory of the data loop. A keyword transformation unit (KXU) is therefore required to enhance the performance of the structure memory. The KXU encodes variable-length keywords into a fixed-length form by hashing. By managing a library of carefully designed hashing algorithms and by dynamically loading the algorithms in a writable control store for execution, the KXU allows the efficient storage of keywords and their associated information and minimizes subsequent accesses to the SM.