Patent ID: 6606626
Filing Date: 2003-08-12
Classification: G06F,Y10S

Abstract:
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.