A hash table for a collection of data items includes a set of hash buckets, each hash bucket being associated with a subset of the collection of data items, and a set of properties entries in each of the hash buckets. Each properties entry includes a pointer to an associated data item in the subset associated with the bucket and a set of representative values identifying the associated data item. A hash table can also include bucket groups defining a second level hash table to permit resizing of the hash table.