Abstract: An improved B-Tree index structure with grouped index leaf pages and computer-implemented method for modifying the same. The improved index may be stored in a B-Tree structure on a data, storage device that may be coupled to a computer, in particular, the improved index may comprise one or more grouped index leaf pages which may store index entries that may be grouped for the same index key value and then later stored as shortened index leaf entries. In addition, a hybrid version of the improved index may be implemented to combine grouped index leaf pages with conventional index leaf pages in a single index. In particular, the intermediate index entries may be extended to store references to both grouped index leaf pages and conventional index leaf pages.