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System and method for performing joins and self-joins in a database system

  • US 5,983,215 A
  • Filed: 05/08/1997
  • Issued: 11/09/1999
  • Est. Priority Date: 05/08/1997
  • Status: Expired due to Fees
First Claim
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1. A method for joining in a database system one or more input tables comprised of records stored in a storage medium using a join index indicative of records to be joined and having an index entry for each record to be included an output resulting from said join, said method comprising the steps of:

  • (a) allocating an array of partitions in a memory responsive to said index entries of each said input table in said join index;

    (b) reading said join index;

    (c) storing said join index entries corresponding to each of said input tables and a corresponding partition identifier to temporary files associated with said allocated partitions;

    (d) reading in turn said index entries and said corresponding partition identifier in each of said temporary files and sorting each said temporary file;

    (e) sequentially reading portions of said tables only if said portion includes a record identified in said sorted temporary file; and

    (f) writing said read records in accordance with an order of said corresponding partition identifiers to separate output files associated with each said input table.

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