Locking Expressions for Increased Database Concurrency
Anthony C. Klug · Journal of the ACM · 1983
Access to a relation R m a relational database is sometimes based on how R joins with other relations rather than on what values appear m the attributes of R-tuples Usmg sunple predicate locks forces the entire relation to be locked m these cases.A technique is presented which allows locking of the smallest possible set oftuples even when the selecuon is based on joins w~th other relauons The algonthms are based on a generalization of tableaux The tableaux used here can represent relational algebra quenes wtth any of the domain companson operators =, #, , and >-..