1. A method for a data processing apparatus of searching data in an ordered list for at least one search value, chunks of the list being labeled by respective chunk labels, the chunk labels being stored in a sparse index and being representative of respective ranges of the data contained in the respective corresponding chunks, the method comprising the steps of: (1) sorting the search values, if there are more than one, in an order that corresponds to the ordering of the list: (2) searching the sparse index for a hit chunk label representative of a range of values to which at least a first search value in the sorted search values belongs; (3) accessing the hit chunk corresponding to the hit chunk label representative of the range of values to which the first search value belongs; and (4) searching the hit chunk for the first search value.