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Database system with lock manager enhancement for improving concurrency

  • US 6,606,626 B1
  • Filed: 02/11/2000
  • Issued: 08/12/2003
  • Est. Priority Date: 10/20/1998
  • Status: Expired due to Term
First Claim
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1. In a database system having a database storing a database table comprising a plurality of data rows, said rows storing information organized into particular database fields, an improved method for scanning a table for particular rows that meet a specified scan criterion, the method comprising:

  • providing each row of the database table with delete and update status flags for indicating which rows may be skipped during the table scan, wherein;

    (i) the update status flag for a row is set when a transaction updates the row and is cleared when the transaction commits, (ii) the delete status flag for a row is set when a transaction deletes a row and is cleared when the transaction rolls back, and (iii) both the update and delete status flags for a row are restored to their respective prior states when a transaction rolls back that had flagged the row as updated;

    tracking column status information for indicating columns that have been modified for a table being updated;

    based on said status flags and said column status information, determining those rows of the database table that may be skipped during the table scan; and

    scanning the database table for rows that meet said specified scan criterion without blocking rows that are determined to be rows that may be skipped.

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