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2.8 KiB
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<!--$Id: intro.so,v 10.22 2000/12/18 21:05:14 bostic Exp $-->
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<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.-->
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<html>
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<title>Berkeley DB Reference Guide: What are the available access methods?</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
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<a name="2"><!--meow--></a>
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<table><tr valign=top>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Access Methods</dl></h3></td>
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<td width="1%"><a href="../../ref/simple_tut/close.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/am_conf/select.html"><img src="../../images/next.gif" alt="Next"></a>
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</td></tr></table>
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<p>
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<h1 align=center>What are the available access methods?</h1>
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<p>Berkeley DB currently offers four access methods: Btree, Hash, Queue and Recno.
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<h3>Btree</h3>
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<p>The Btree access method is an implementation of a sorted, balanced tree
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structure. Searches, insertions, and deletions in the tree all take O(log
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base_b N) time, where base_b is the average number of keys per page, and
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N is the total number of keys stored. Often, inserting ordered data into
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Btree implementations results in pages that are only half-full. Berkeley DB
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makes ordered (or inverse ordered) insertion the best case, resulting in
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nearly full-page space utilization.
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<h3>Hash</h3>
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<p>The Hash access method data structure is an implementation of Extended
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Linear Hashing, as described in "Linear Hashing: A New Tool for File and
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Table Addressing", Witold Litwin, <i>Proceedings of the 6th
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International Conference on Very Large Databases (VLDB)</i>, 1980.
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<h3>Queue</h3>
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<p>The Queue access method stores fixed-length records with logical record
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numbers as keys. It is designed for fast inserts at the tail and has a
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special cursor consume operation that deletes and returns a record from
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the head of the queue. The Queue access method uses record level locking.
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<h3>Recno</h3>
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<p>The Recno access method stores both fixed and variable-length records with
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logical record numbers as keys, optionally backed by a flat text (byte
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stream) file.
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<table><tr><td><br></td><td width="1%"><a href="../../ref/simple_tut/close.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/am_conf/select.html"><img src="../../images/next.gif" alt="Next"></a>
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<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font>
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