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System and method for query optimization using quantile values of a large unordered data set

  • US 5,664,171 A
  • Filed: 04/14/1994
  • Issued: 09/02/1997
  • Est. Priority Date: 04/14/1994
  • Status: Expired due to Fees
First Claim
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1. A data storage system, comprising:

  • a computer;

    one or more input devices electrically connected to the computer for generating a user request for data satisfying a predetermined condition;

    a database accessible by the computer for holding a set of data records; and

    a database management system executable by the computer, the database management system including a compiler, the compiler including;

    a query optimizer for generating a query plan in response to quantiles of the set of data records;

    comparator means in the query optimizer for sequentially comparing the data records in the set of data records to a test value of the condition in a single pass over the set of data records;

    means for selectively inserting a data record in a test set having a cardinality less than the cardinality of the set of data records based upon the comparison and the condition; and

    means for accessing the test set to generate a quantile value in response to a data record in the test set, the quantile value representative of a number of data records in the database satisfying the condition.

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