ch12 - Chapter12:IndexingandHashing Rev.Sep17,2008

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Database System Concepts, 5th Ed . ©Silberschatz, Korth and Sudarshan See  www.db-book.com  for conditions on re-use  Chapter 12: Indexing and Hashing Chapter 12: Indexing and Hashing Rev. Sep 17, 2008
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©Silberschatz, Korth and Sudarshan 12.2 Database System Concepts - 5 th  Edition. Chapter 12:  Indexing and Hashing Chapter 12:  Indexing and Hashing Basic Concepts Ordered Indices  B + -Tree Index Files B-Tree Index Files Static Hashing Dynamic Hashing  Comparison of Ordered Indexing and Hashing  Index Definition in SQL Multiple-Key Access
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©Silberschatz, Korth and Sudarshan 12.3 Database System Concepts - 5 th  Edition. Basic Concepts 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
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©Silberschatz, Korth and Sudarshan 12.4 Database System Concepts - 5 th  Edition. Index Evaluation Metrics Index Evaluation Metrics Access types supported efficiently.  E.g.,  records with a specified value in the attribute or records with an attribute value falling in a specified range  of values (e.g.  10000 <  salary  < 40000) Access time Insertion time Deletion time Space overhead
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©Silberschatz, Korth and Sudarshan 12.5 Database System Concepts - 5 th  Edition. Ordered Indices Ordered Indices In an  ordered index index entries are stored sorted on the  search key value.  E.g., author catalog in library. Primary index in a sequentially ordered file, the index whose  search key specifies the sequential order of the file. Also called  clustering index The search key of a primary index is usually but not  necessarily the primary key. Secondary index :   an index whose search key specifies an  order different from the sequential order of the file.  Also called  non-clustering index . Index-sequential file :  ordered sequential file with a primary  index.
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12.6 Database System Concepts - 5 th  Edition.
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ch12 - Chapter12:IndexingandHashing Rev.Sep17,2008

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