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Dense Index

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Definition

Consider a tree-based index on some numeric attribute A of a relation R. This index is called dense if every search-key value of attribute A in relation R also appears in the index. Hence for every search-key value x in A, there is an index record of the form <x, pointer>, where pointer points to the first record (if many such exist) in relation R that has R.A = x.

Key Points

Tree-based indices are built on numeric attributes and maintain an order among the indexed search-key values. Hence, they provide efficient access to the records of a relation by attribute value. Consider for example an index built on attribute A of relation R. The leaf pages of the index contain index-records of the form <search-key, pointer>, where search-key corresponds to a value from the indexed attribute A and pointer points to the respective record in the indexed relation R with that attribute value. If all distinct values that appear in R.A also appear in index records, this index is dense,...

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Recommended Reading

  1. Elmasri R. and Navathe S.B. Fundamentals of Database Systems, 5th edn. Addisson-Wesley, Boston, MA, 2007.

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  2. Manolopoulos Y., Theodoridis Y., and Tsotras V.J. Advanced Database Indexing. Kluwer, Dordecht, 1999.

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  3. Silberschatz A., Korth H.F., and Sudarshan S. Database System Concepts, 5th edn. McGraw-Hill, New York, 2006.

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© 2009 Springer Science+Business Media, LLC

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Moro, M.M., Tsotras, V.J. (2009). Dense Index. In: LIU, L., ÖZSU, M.T. (eds) Encyclopedia of Database Systems. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-39940-9_760

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