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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>67.1. 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 Vsnapshot" /><link rel="prev" href="btree.html" title="Chapter 67. B-Tree Indexes" /><link rel="next" href="btree-behavior.html" title="67.2. Behavior of B-Tree Operator Classes" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">67.1. Introduction</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="btree.html" title="Chapter 67. B-Tree Indexes">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="btree.html" title="Chapter 67. B-Tree Indexes">Up</a></td><th width="60%" align="center">Chapter 67. B-Tree Indexes</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="btree-behavior.html" title="67.2. Behavior of B-Tree Operator Classes">Next</a></td></tr></table><hr /></div><div class="sect1" id="BTREE-INTRO"><div class="titlepage"><div><div><h2 class="title" style="clear: both">67.1. 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" title="Chapter 67. B-Tree Indexes">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="btree.html" title="Chapter 67. B-Tree Indexes">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="btree-behavior.html" title="67.2. Behavior of B-Tree Operator Classes">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 67. B-Tree Indexes </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 67.2. Behavior of B-Tree Operator Classes</td></tr></table></div></body></html>