external index

(data structure)

Definition: An auxiliary data structure added to a main data structure to improve operations, such as a search on a secondary key.

See also inverted index, hash table, search tree.

Note: The implementation probably embeds parts of the external index in the primary data structure, such as adding a few fields to each node. If items are added to or deleted from the primary data structure, the external index must be maintained, too. Data may have multiple external indexes, such as a data base of movies with inverted indexes for title, actors, and genre.

Author: PEB

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Entry modified 17 December 2004.
HTML page formatted Wed Mar 13 12:42:45 2019.

Cite this as:
Paul E. Black, "external index", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed. 17 December 2004. (accessed TODAY) Available from: