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United States Patent [w]
Srivastava et al.
US006032144A [ii] Patent Number: 6,032,144  Date of Patent: *Feb. 29,2000
 OPTIMIZATION OF QUERIES USING RELATIONAL ALGEBRAIC THETASEMLJOIN OPERATOR
 Inventors: Divesh Srivastava, New Providence, N.J.; Peter J. Stuckey, Elwood, Australia; Sundararajarao Sudarshan,
 Assignee: Lucent Technologies Inc., Murray Hill, N.J.
[ * ] Notice: This patent is subject to a terminal disclaimer.
 Appl. No.: 08/862,459  Filed: May 23, 1997
Related U.S. Application Data
 Provisional application No. 60/018,391, May 29, 1996.
 Int. C I. G06F 17/30
 U.S. CI 707/3; 707/2; 707/4; 707/5
 Field of Search 707/1, 2, 3, 4,
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Primary Examiner—-Wayne Amsbury
Assistant Examiner—Srirama Channavajjala
Attorney, Agent, or Firm—Geraldine D. Monteleone
A collection ol equivalence rules involving the multiset version ol the relational algebraic theta-semijoin operator is used to generate relational algebraic expressions equivalent to a computer programming language query. These expressions may be employed as a search space which is utilized by, for example, optimizing software or software that determines the equivalency ol queries. Cost formulas for the multiset version ol the theta-semijoin operator may be used in computing cost estimates for the generated expressions. Based on these computed cost estimates, the least costly implementation ol a complex query is determined. Thus, queries are cost-based optimized on both a local and global basis by use ol the relational algebraic theta-semijoin operator.
22 Claims, 2 Drawing Sheets
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