Unisys Corporation

Michael S Jende

James M Plasek

Kelsey L Bruso

Lee-Chin Hsu Liu

Jennifer J Smith

Ronald H Menzhuber

Kenji Yoneda

Lowell L Baerenwald

Altering tables in a database system may be difficult because the tables may only be altered when all connection to the tables have been released. A free resources parameter may be set on in a management system for the database system to specify that resources should be attempted to be released. Connections to the database may be closed earlier than conventionally closed. For example, connections that are idle may be released. Once the connections have been released the database may be altered and the free resources parameter turned off. The free resources parameter notifies the database system of a pending alteration and allows the database to gracefully close connections to provide an opportunity for the alteration to occur.

Free resources parameter for improving performance of database alterations

A system and method is provided for inserting an ascending or descending sequence of data records into a database table represented by a tree structure. A search is performed to locate a node of the tree that includes the insertion point for a record in the sequence. If the node must be divided to store the record, it is determined whether division of the node at the insertion point will prevent a subsequently received record in the sequence from being stored on the same node with other records in the sequence irrespective of the storage space available on that node. If so, the node division is performed so that a record that is not in the sequence but that is adjacent to the insertion point is maintained on the same node as the other records in the sequence.

Database management system and method for maintaining a database in a range sensitive manner

A hybrid hash join process joins data rows from two tables which have at least one common data column by partitioning the data rows based on the values in the common data column(s), creating data structures to decrease search time for matching rows, and recovering full data buffers using a unique buffer management methodology. A smaller one of the two tables is designated as an outer table and a larger one of the two tables as an inner table. The hybrid hash join process determines which rows in the inner and outer tables satisfy a selection criteria; the rows that satisfy the selection criteria are referred to as inner hit rows and outer hit rows. The hybrid hash join process assigns the inner and outer hit rows to corresponding inner and outer partitions, respectively. Buffer overflow in the outer partitions is handled by linking empty buffers to the outer partitions until all buffers are used. Buffer space is recovered by writing outer hit rows for a selected partition to mass storage. Buffer overflow in the inner partitions is handled by either writing the inner rows in the buffer to mass storage or by searching the corresponding outer partition for matches. The outer hit rows in the corresponding outer partition are allocated to entries in a data structure which is then probed to find matches for the inner hit rows in the buffer. Matching outer hit rows for any inner hit rows written to mass storage are found by repeatedly reading into memory inner and outer hit rows and probing a data structure created from the memory-resident outer hit rows in a partition. Optionally, binary trees are built from the entries in the data structure to speed up the probing procedure. The hybrid hash join process uses at least one hashing algorithm to assign hit rows to partitions, to allocate rows to entries in the data structures, and to probe the data structures for matches.

Hybrid hash join process

Growing community of inventors

White Bear Lake, MN, United States of America

Michael S Jende