International Business Machines Corporation

Richard W Hedges

Yun Yu Wang

Balakrishna Raghavendra Iyer

Chandrasekaran Mohan

Josephine Miu Cheng

Donald J Haderle

Serge Boivin

Michael J Cincinatus

K Bernhard Schiefer

Margaret H Li

A method for externalizing database monitor information, and a database management system incorporating the method, which utilizes the database system's own data manipulation and retrieval system is disclosed. Monitor information is logically available in pseudotable form which may be accessed as any other data. However pseudotables do not actually exist; rather the result set is constructed when a request is made to select from a pseudotable. A predefined format for each pseudotables is stored in the database catalog tables and is used in constructing the tuples from existing internal data structures which are constantly updated with monitor data.

Utilizing pseudotables as a method and mechanism providing database

Results of a relational data base management system are joined in a process requiring, first, existence of an index on the join columns of the inner table, and, second, ordering on the join column of the first table. First, the index on the inner table's join column is scanned for rows of the inner table having join column values matching such values of rows in the outer table. This is done in a single pass through the outer table. Next, a temporary work table containing the identifiers of inner table rows having join column values matching those of the outer table is produced by concatenating the row identifiers to their matching outer table rows. Following this, the temporary work table is ordered by the identifiers. Last, the identifier list of inner table rows is used to retrieve the corresponding rows of the inner table. All predicates local to the inner table are applied to the retrieved rows, and those satisfying these local predicates are combined with their matching outer table rows and returned to the user.

Hybrid technique for joining tables

Growing community of inventors

Mississauga, Canada

Richard W Hedges