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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 id="docContent" class="container-fluid col-10"><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 13.4 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 xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="btree.html" title="Chapter 63. B-Tree Indexes">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="btree.html" title="Chapter 63. B-Tree Indexes">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="btree-behavior.html" title="63.2. Behavior of B-Tree Operator Classes">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" title="PostgreSQL 13.4 Documentation">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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