Sparse Index Files (Cont.) Compared to dense indices: Less space and less maintenance overhead for insertions and deletions. Generally slower than dense index for locating records. ■Good tradeoff: for clustered index:sparse index with an index entry for every block in file, corresponding to least search-key value in the block. data block 0 data block 1 For unclustered index:sparse index on top of dense index(multilevel index) Database System Concepts-7th Edition 14.9 @Silberschatz,Korth and SudarshanDatabase System Concepts - 7 14.9 ©Silberschatz, Korth and Sudarshan th Edition Sparse Index Files (Cont.) ▪ Compared to dense indices: • Less space and less maintenance overhead for insertions and deletions. • Generally slower than dense index for locating records. ▪ Good tradeoff: • for clustered index: sparse index with an index entry for every block in file, corresponding to least search-key value in the block. • For unclustered index: sparse index on top of dense index (multilevel index)