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Efficient interaction among cost-based transformations

  • US 7,702,627 B2
  • Filed: 03/08/2007
  • Issued: 04/20/2010
  • Est. Priority Date: 06/22/2004
  • Status: Active Grant
First Claim
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1. A method of transforming a certain query, comprising:

  • making a determination of whether or not to rewrite the certain query using a first transformation, wherein the determination includes;

    applying the first transformation to the certain query to generate a first query;

    generating a second query based on the first query by applying a second transformation;

    determining a query execution cost of the second query; and

    making the determination based on the query execution cost of the second query;

    wherein query execution costs are determined for two or more semantically equivalent queries, the two or more semantically equivalent queries including at least the certain query and the second query;

    wherein a candidate execution plan is generated for each semantically equivalent query of the two or more semantically equivalent queries; and

    wherein the candidate execution plan for each semantically equivalent query of the two or more semantically equivalent queries is different than the candidate execution plan for each other semantically equivalent query of the two or more semantically equivalent queries;

    wherein the steps of applying, generating, determining, and making the determination are performed by one or more computing devices.

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