Arrangement for filtering data item updates to reduce the number of updates to a data item to be stored on mass data storage facility

A method of filtering data item updates provided by a data item update source, each data item update having an associated data item identifier having a data item identification value, and providing selected ones of said data item updates to a downstream data item utilization subsystem, the method comprising the steps of:

• A. providing a filter queue including a plurality of queue elements extending from a head queue element, each queue element including a data item update received from said data item update source;
• B. providing a data item identifier table for storing, for the data item identification values associated with data item updates in the filter queue, a pointer to the one of the queue elements containing the most recently received data item update for the particular data item identification value;
• and
• C. selectively coupling the data item update from the head queue element for use by the downstream data item utilization subsystem if the head queue element is pointed to by one of said pointers associated with the data item identification value of the data item update in the head queue element the data item update selection element otherwise not coupling the data item update from the head queue element for use by the downstream data utilization subsystem.

A filter for filtering data item updates provided by a data item update source, each data item update having an associated data item identifier having a data item identification value, the filter providing selected ones of said data item updates to a downstream data item utilization subsystem, the filter comprising:

• A. a digital data processor;
• and
• B. a control subsystem for controlling the processor, the control subsystem comprising:
• i. a filter queue module for enabling the processor to maintain a filter queue comprising including a plurality of queue elements extending from a head queue element, each queue element including a data item update received from said data item update source;
• ii. a data item identifier table module for enabling said processor to maintain a data item identifier table for storing, for the data item identification values associated with data item updates in the filter queue, a pointer to the one of the queue elements containing the most recently received data item update for the particular data item identification value;
• and
• iii. a data item update selection module for enabling the processor to selectively couple the data item update from the head queue element for use by the downstream data item utilization subsystem if the head queue element is pointed to by one of said pointers associated with the data item identification value of the data item update in the head queue element, and otherwise not couple the data item update from the head queue element for use by the downstream data utilization subsystem.

A control subsystem for controlling a digital data processor to form a filter, the filter filtering data item updates provided by a data item update source, each data item update having an associated data item identifier having a data item identification value, the filter providing selected ones of said data item updates to a downstream data item utilization subsystem, control subsystem comprising:

• A. a filter queue module for enabling the processor to maintain a filter queue comprising including a plurality of queue elements, each queue element including a data item update received from said data item update source;
• B. a data item identifier table module for enabling said processor to maintain a data item identifier table for storing, for the data item identification values associated with data item updates in the filter queue, a pointer to the one of the queue elements containing the most recently received data item update for the particular data item identification value;
• and
• C. a data item update selection module for enabling the processor to selectively couple the data item update from the head queue element for use by the downstream data item utilization subsystem if the head queue element is pointed to by one of said pointers associated with the data item identification value of the data item update in the head queue elements and otherwise not couple the data item update from the head queue element for use by the downstream data utilization subsystem.