<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!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 Vsnapshot" /><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 11.5 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>
