The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 01, 2000
Filed:
Dec. 11, 1996
Pedro Celis, Austin, TX (US);
Diana Shak, San Jose, CA (US);
Jay Vaishnav, Cupertino, CA (US);
Hansjorg Zeller, Los Altos, CA (US);
Tandem Computers, Inc., Cupertino, CA (US);
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.