Concurrency control in materialized views of a database

摘要

In a database, a database manager can generate a view, which, in concept, is a subset of the database, which is placed outside the database for use without disturbing the database, and without disturbance by others using the database. The subset, or view, can be understood as a collection of rows, or tuples, of data copied from the database. With views existing, multiple copies of data within the database now exist: the original in the database, and copies in the views. If one of these is changed, without corresponding changes made in the others, then inconsistencies occur, which cannot be tolerated. Under the invention, when a user seeks a lock on a view, indicating that a change may be imminent, the invention locks a superset of the tuples in the database from which the view is derived. A superset is a set which contains the set of tuples of the view, plus possibly others. Thus, more tuples are locked than strictly necessary. The excess locking is tolerated because other benefits are obtained.