Comparison of Partitioning Techniques(Cont.) Hash partitioning: Good for sequential access Assuming hash function is good,and partitioning attributes form a key,tuples will be equally distributed between disks Retrieval work is then well balanced between disks. Good for point queries on partitioning attribute Can lookup single disk,leaving others available for answering other queries. Index on partitioning attribute can be local to disk,making lookup and update more efficient No clustering,so difficult to answer range queries Database System Concepts-6th Edition 18.9 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 6 18.9 ©Silberschatz, Korth and Sudarshan th Edition Hash partitioning: Good for sequential access Assuming hash function is good, and partitioning attributes form a key, tuples will be equally distributed between disks Retrieval work is then well balanced between disks. Good for point queries on partitioning attribute Can lookup single disk, leaving others available for answering other queries. Index on partitioning attribute can be local to disk, making lookup and update more efficient No clustering, so difficult to answer range queries Comparison of Partitioning Techniques (Cont.)