Comparison of Partitioning Techniques(Cont.) Range partitioning: Provides data clustering by partitioning attribute value. Good for sequential access Good for point queries on partitioning attribute:only one disk needs to be accessed. For range queries on partitioning attribute,one to a few disks may need to be accessed Remaining disks are available for other queries. Good if result tuples are from one to a few blocks. If many blocks are to be fetched,they are still fetched from one to a few disks,and potential parallelism in disk access is wasted Example of execution skew. Database System Concepts-6th Edition 18.10 @Silberschatz,Korth and SudarshanDatabase System Concepts - 6 18.10 ©Silberschatz, Korth and Sudarshan th Edition Comparison of Partitioning Techniques (Cont.) Range partitioning: Provides data clustering by partitioning attribute value. Good for sequential access Good for point queries on partitioning attribute: only one disk needs to be accessed. For range queries on partitioning attribute, one to a few disks may need to be accessed Remaining disks are available for other queries. Good if result tuples are from one to a few blocks. If many blocks are to be fetched, they are still fetched from one to a few disks, and potential parallelism in disk access is wasted  Example of execution skew