The AddResultItemToResults method can be overridden to enable result filtering, but since that method is called early in the search process, it will include many results that will not actually be shown to the user (i.e. results on page 2 onwards). Therefore, it is preferable to load as little data for each document at this stage (since the document may not be presented as a result).

If no filtering is required, set this to DocId, for optimal search speed.