Encyclopedia of Database Systems

Editors: LING LIU, M. TAMER ÖZSU

Dense Index

  • Mirella M. Moro
  • Vassilis J. Tsotras
Reference work entry
DOI: https://doi.org/10.1007/978-0-387-39940-9_760

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. 1.
    Elmasri R. and Navathe S.B. Fundamentals of Database Systems, 5th edn. Addisson-Wesley, Boston, MA, 2007.Google Scholar
  2. 2.
    Manolopoulos Y., Theodoridis Y., and Tsotras V.J. Advanced Database Indexing. Kluwer, Dordecht, 1999.Google Scholar
  3. 3.
    Silberschatz A., Korth H.F., and Sudarshan S. Database System Concepts, 5th edn. McGraw-Hill, New York, 2006.Google Scholar

Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Mirella M. Moro
    • 1
  • Vassilis J. Tsotras
    • 2
  1. 1.Federal University of Rio Grande do SulPorte AlegreBrazil
  2. 2.University of California-RiversideRiversideUSA