Managing Counter Saturation In A Filter

Filters and methods for managing presence counter saturation are disclosed. The filters can be coupled to a collection of items and maintain information for determining a potential presence of an identified item in the collection of items. The filter includes a filter controller and one or more mapping functions. Each mapping function has a plurality of counters associated with the respective mapping function. When a membership status of an item in the collection of items changes, the filter receives a membership change notification including an identifier identifying the item. Each mapping function processes the identifier to identify a particular counter associated with the respective mapping function. If a particular counter has reached a predetermined value, a request including a reference to the particular counter is sent to the collection of items. The filter receives a response to the request and modifies the particular counter as a result of the response.