Data processing: database and file management or data structures – Database design – Data structure types
Patent
1996-12-11
2000-02-01
Choules, Jack M.
Data processing: database and file management or data structures
Database design
Data structure types
G06F 1730
Patent
active
060214058
ABSTRACT:
A system and method for optimizing a database query with improved performance enhancements is herein disclosed. The database query consists of one or more logical expressions. Through the repeated application of one or more rules, the logical expressions are transformed into execution plans. The query optimizer partitions the database query into one or more subproblems with each subproblem consisting of one or more logical expressions. A plan is obtained for each subproblem with the plan for the database query including the plans for each subproblem. The query optimizer is cost-based and uses rules including transformation and implementation rules that are used to perform transformations on the logical expressions in a subproblem in order to produce a plan. The rules are classified into context-free and context-sensitive in order to avoid generating duplicate expressions. Context-free rules are applied once for each logical expression and context-sensitive rules are applied once for each logical expression for a particular optimization goal. In a preferred embodiment, the query optimizer performs several optimization passes over the database query in order to obtain an optimal plan. For each pass, if no optimal plan exists for the requested optimization goal, existing plans having the same optimization goal are utilized with each input reoptimized for a more cost effective plan.
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Kim, H., Lee S. "Tree Query Optimization in Distributed Object Oriented Databases", IEEE pp. 45-52, Apr. 1994.
Galindo-Legaria, "Algebraic Optimization of Outerjoin Queries", Ph.D. dissertation, Center for Research in Computing Technology, Harvard University, Cambrige, Ma, 1992.
Celis Pedro
Shak Diana
Vaishnav Jay
Zeller Hansjorg
Choules Jack M.
Tandem Computers Inc.
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