Basic Concepts Indexing mechanisms used to speed up access to desired data. E.g.,author catalog in library Search Key -attribute to set of attributes used to look up records in a file. An index file consists of records(called index entries)of the form search-key pointer Index files are typically much smaller than the original file Two basic kinds of indices: Ordered indices:search keys are stored in sorted order Hash indices:search keys are distributed uniformly across “buckets”using a“nash function”. Database System Concepts-5th Edition,Oct 4,2006 12.3 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 5 12.3 ©Silberschatz, Korth and Sudarshan th Edition, Oct 4, 2006 Basic Concepts Indexing mechanisms used to speed up access to desired data. E.g., author catalog in library Search Key - attribute to set of attributes used to look up records in a file. An index file consists of records (called index entries) of the form Index files are typically much smaller than the original file Two basic kinds of indices: Ordered indices: search keys are stored in sorted order Hash indices: search keys are distributed uniformly across “buckets” using a “hash function”. search-key pointer