eXtremeDB, like other databases, provides indexes for access to objects based on key values. An index definition consists of any combination of scalar fields, structure elements or vector elements from a given class. Indexes can be of various types, the most common of which are either hash or tree (BTree). Tree indexes can have a mix of ascending and descending components and, in addition to exact-match searches, can be used for sorting and range-based retrieval. Hash indexes are used for fast storage and retrieval but without sorting or range-based access. Both tree and hash indexes can be declared unique or nonunique to exclude or allow duplicate values.
eXtremeDB also provides a number of specialized indexes that optimize access to records and groups of records for particular types of applications, such as the following:
Patricia Trie: Particularly useful for network and telecommunications applications, these are often used to quickly perform IP address prefix
matching for IP subnet, network or routing table lookups.
R-Tree: These indexes are commonly used to index latitude/longitude and speed spatial searches; for example to find the rectangle that bounds a given point, or all rectangles that overlap a specified rectangle.
Kd-Tree: Using a data structure for organizing points in a k-dimensional space, kd-trees speed lookups that involve a multidimensional search key, and are most commonly used in query-by-form and query-by-example cases.
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