Repository data intervals are determined as similar to an input data interval. Repository digests corresponding to the similar repository data interval are loaded into a sequential representation and into a search structure. Matches of input digests and the repository digests are found using the search structure. Each one of the found matches of the input digests and repository digests are extended using the sequential representation. Data matches are determined between the input data and the repository data using extended matches of digests. A compact index pointing to a position in the sequential representation of digests is incorporated into entries of the search structure.