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APPARATUS, SYSTEM, AND METHOD FOR PERFORMING FAST APPROXIMATE COMPUTATION OF STATISTICS ON QUERY EXPRESSIONS

  • US 20080172354A1
  • Filed: 01/12/2007
  • Published: 07/17/2008
  • Est. Priority Date: 01/12/2007
  • Status: Active Grant
First Claim
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1. A computer program product comprising a computer readable medium having:

  • computer usable program code programmed to perform fast approximate computation of statistics on query expressions within a database management system (DBMS) by accurately estimating the sizes of intermediate query results based on frequency statistics, the operations of the computer program product comprising;

    analyzing a query expression for join instructions;

    identifying a fact table and a dimension table from the join instructions;

    retrieving frequency statistics from a catalog table corresponding to distinct values within one or more join columns of the fact table;

    generating a frequency statistics table comprising the frequency statistics retrieved from the catalog table;

    estimating frequency statistics corresponding to each column of a join result between the fact table and the dimension table by generating a statistical view comprising a join of the generated frequency statistics table and the dimension table by using the generated frequency statistics table to simulate the fact table; and

    populating the statistical view with the estimated frequency statistics.

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