<?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>52.33. pg_opclass</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="catalog-pg-namespace.html" title="52.32. pg_namespace" /><link rel="next" href="catalog-pg-operator.html" title="52.34. pg_operator" /></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">52.33. <code xmlns="http://www.w3.org/1999/xhtml" class="structname">pg_opclass</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalog-pg-namespace.html" title="52.32. pg_namespace">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="catalogs.html" title="Chapter 52. System Catalogs">Up</a></td><th width="60%" align="center">Chapter 52. System Catalogs</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="catalog-pg-operator.html" title="52.34. pg_operator">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="CATALOG-PG-OPCLASS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">52.33. <code class="structname">pg_opclass</code></h2></div></div></div><a id="id-1.10.4.35.2" class="indexterm"></a><p> The catalog <code class="structname">pg_opclass</code> defines index access method operator classes. Each operator class defines semantics for index columns of a particular data type and a particular index access method. An operator class essentially specifies that a particular operator family is applicable to a particular indexable column data type. The set of operators from the family that are actually usable with the indexed column are whichever ones accept the column's data type as their left-hand input. </p><p> Operator classes are described at length in <a class="xref" href="xindex.html" title="38.15. Interfacing Extensions To Indexes">Section 38.15</a>. </p><div class="table" id="id-1.10.4.35.5"><p class="title"><strong>Table 52.33. <code class="structname">pg_opclass</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_opclass Columns" border="1"><colgroup><col /><col /><col /><col /></colgroup><thead><tr><th>Name</th><th>Type</th><th>References</th><th>Description</th></tr></thead><tbody><tr><td><code class="structfield">oid</code></td><td><code class="type">oid</code></td><td> </td><td>Row identifier (hidden attribute; must be explicitly selected)</td></tr><tr><td><code class="structfield">opcmethod</code></td><td><code class="type">oid</code></td><td><code class="literal"><a class="link" href="catalog-pg-am.html" title="52.3. pg_am"><code class="structname">pg_am</code></a>.oid</code></td><td>Index access method operator class is for</td></tr><tr><td><code class="structfield">opcname</code></td><td><code class="type">name</code></td><td> </td><td>Name of this operator class</td></tr><tr><td><code class="structfield">opcnamespace</code></td><td><code class="type">oid</code></td><td><code class="literal"><a class="link" href="catalog-pg-namespace.html" title="52.32. pg_namespace"><code class="structname">pg_namespace</code></a>.oid</code></td><td>Namespace of this operator class</td></tr><tr><td><code class="structfield">opcowner</code></td><td><code class="type">oid</code></td><td><code class="literal"><a class="link" href="catalog-pg-authid.html" title="52.8. pg_authid"><code class="structname">pg_authid</code></a>.oid</code></td><td>Owner of the operator class</td></tr><tr><td><code class="structfield">opcfamily</code></td><td><code class="type">oid</code></td><td><code class="literal"><a class="link" href="catalog-pg-opfamily.html" title="52.35. pg_opfamily"><code class="structname">pg_opfamily</code></a>.oid</code></td><td>Operator family containing the operator class</td></tr><tr><td><code class="structfield">opcintype</code></td><td><code class="type">oid</code></td><td><code class="literal"><a class="link" href="catalog-pg-type.html" title="52.62. pg_type"><code class="structname">pg_type</code></a>.oid</code></td><td>Data type that the operator class indexes</td></tr><tr><td><code class="structfield">opcdefault</code></td><td><code class="type">bool</code></td><td> </td><td>True if this operator class is the default for <code class="structfield">opcintype</code></td></tr><tr><td><code class="structfield">opckeytype</code></td><td><code class="type">oid</code></td><td><code class="literal"><a class="link" href="catalog-pg-type.html" title="52.62. pg_type"><code class="structname">pg_type</code></a>.oid</code></td><td>Type of data stored in index, or zero if same as <code class="structfield">opcintype</code></td></tr></tbody></table></div></div><br class="table-break" /><p> An operator class's <code class="structfield">opcmethod</code> must match the <code class="structname">opfmethod</code> of its containing operator family. Also, there must be no more than one <code class="structname">pg_opclass</code> row having <code class="structname">opcdefault</code> true for any given combination of <code class="structname">opcmethod</code> and <code class="structname">opcintype</code>. </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="catalog-pg-namespace.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="catalogs.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="catalog-pg-operator.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">52.32. <code class="structname">pg_namespace</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 52.34. <code class="structname">pg_operator</code></td></tr></table></div></body></html>
