title: Optimization Using Tuple Subsumption.
creator: Harinarayan, V.
creator: Gupta, A.
subject: Query Processing
description: A tuple t 1 of relation R subsumes tuple t 2 of R, with respect to a query Q if for every database, tuple t 1 derives all, and possibly more, answers to query Q than derived by tuple t 2 . Therefore, the subsumed tuple t 2 can be ignored with respect to Q in the presence of tuple t 1 in relation R. This property finds use in a large number of problems. For instance: during query optimization subsumed tuples can be ignored thereby avoiding the computation of redundant answers; the size of cached information in distributed and object oriented systems can be reduced by omitting subsumed tuples; constraints need not be checked and rules need not be recomputed when provably subsumed updates are made. We give algorithms for deciding effciently when a tuple subsumes another tuple for queries that use arbitrary mathematical functions. We characterize queries for which, whenever a set of tuples T subsumes a tuple t then one of the tuples in T also subsumed t, yielding effciently verifiable cases of subsumption.
publisher: Stanford InfoLab
date: 1994
type: Techreport
type: NonPeerReviewed
format: application/pdf
identifier: http://ilpubs.stanford.edu:8090/60/1/1994-26.pdf
identifier: Harinarayan, V. and Gupta, A. (1994) Optimization Using Tuple Subsumption. Technical Report. Stanford InfoLab. (Publication Note: Appeared in 5th International Conference on Database Theory, Prague, Czech Republic, January 11-13, 1995 (ICDT 1995))
relation: http://ilpubs.stanford.edu:8090/60/