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- <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>63.1. Introduction</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="btree.html" title="Chapter 63. B-Tree Indexes" /><link rel="next" href="btree-behavior.html" title="63.2. Behavior of B-Tree Operator Classes" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">63.1. Introduction</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="btree.html" title="Chapter 63. B-Tree Indexes">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="btree.html" title="Chapter 63. B-Tree Indexes">Up</a></td><th width="60%" align="center">Chapter 63. B-Tree Indexes</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="btree-behavior.html" title="63.2. Behavior of B-Tree Operator Classes">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="BTREE-INTRO"><div class="titlepage"><div><div><h2 class="title" style="clear: both">63.1. Introduction</h2></div></div></div><p>
- <span class="productname">PostgreSQL</span> includes an implementation of the
- standard <acronym class="acronym">btree</acronym> (multi-way balanced tree) index data
- structure. Any data type that can be sorted into a well-defined linear
- order can be indexed by a btree index. The only limitation is that an
- index entry cannot exceed approximately one-third of a page (after TOAST
- compression, if applicable).
- </p><p>
- Because each btree operator class imposes a sort order on its data type,
- btree operator classes (or, really, operator families) have come to be
- used as <span class="productname">PostgreSQL</span>'s general representation
- and understanding of sorting semantics. Therefore, they've acquired
- some features that go beyond what would be needed just to support btree
- indexes, and parts of the system that are quite distant from the
- btree AM make use of them.
- </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="btree.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="btree.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="btree-behavior.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 63. B-Tree Indexes </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 63.2. Behavior of B-Tree Operator Classes</td></tr></table></div></body></html>
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