Compressed Text Databases with Efficient Query Algorithms Based on the Compressed Suffix Array

A compressed text database based on the compressed suffix array is proposed. The compressed suffix array of Grossi and Vitter occupies only O(n) bits for a text of length n; however it also uses the text itself that occupies O(n log |Σ|) bits for the alphabet Σ. On the other hand, our data structure does not use the text itself, and supports important operations for text databases: inverse, search and decompress. Our algorithms can find occ occurrences of any substring P of the text in O(|P | logn + occ logǫ n) time and decompress a part of the text of length l in O(l+logǫ n) time for any given 1 ≥ ǫ > 0. Our data structure occupies only n( 2 ǫ ( 3 2 +H0+2 logH0)+2+ 4 log n logǫ n−1 )+o(n)+O(|Σ| log |Σ|) bits where H0 ≤ log |Σ| is the order-0 entropy of the text. We also show the relationship with the opportunistic data structure of Ferragina and Manzini.