Reference Work Entry

Encyclopedia of Database Systems

pp 197-200


  • Donghui ZhangAffiliated withNortheastern University
  • , Kenneth Paul BaclawskiAffiliated withNortheastern University
  • , Vassilis J. TsotrasAffiliated withUniversity of California-Riverside




The B+-tree is a disk-based, paginated, dynamically updateable, balanced, and tree-like index structure. It supports the exact match query as well as insertion/deletion operations in O(logpn) I/Os, where n is the number of records in the tree and p is the page capacity in number of records. It also supports the range searches in O(logpn + tp) I/Os, where t is the number of records in the query result.

Historical Background

The binary search tree is a well-known data structure. When the data volume is so large that the tree does not fit in main memory, a disk-based search tree is necessary. The most commonly used disk-based search trees are the B-tree and its variations. Originally invented by Bayer and McCreight [2], the B-tree may be regarded as an extension of the balanced binary tree, since a B-tree is always balanced (i.e., all leaf nodes are on the same level). Since each disk access retrieves or updates an entire bloc ...

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