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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>52.3. pg_am</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-aggregate.html" title="52.2. pg_aggregate" /><link rel="next" href="catalog-pg-amop.html" title="52.4. pg_amop" /></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">52.3. <code xmlns="http://www.w3.org/1999/xhtml" class="structname">pg_am</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalog-pg-aggregate.html" title="52.2. pg_aggregate">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-amop.html" title="52.4. pg_amop">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="CATALOG-PG-AM"><div class="titlepage"><div><div><h2 class="title" style="clear: both">52.3. <code class="structname">pg_am</code></h2></div></div></div><a id="id-1.10.4.5.2" class="indexterm"></a><p>
The catalog <code class="structname">pg_am</code> stores information about
relation access methods. There is one row for each access method supported
by the system.
Currently, only indexes have access methods. The requirements for index
access methods are discussed in detail in <a class="xref" href="indexam.html" title="Chapter 61. Index Access Method Interface Definition">Chapter 61</a>.
</p><div class="table" id="id-1.10.4.5.4"><p class="title"><strong>Table 52.3. <code class="structname">pg_am</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_am 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">amname</code></td><td><code class="type">name</code></td><td> </td><td>Name of the access method</td></tr><tr><td><code class="structfield">amhandler</code></td><td><code class="type">regproc</code></td><td><code class="literal"><a class="link" href="catalog-pg-proc.html" title="52.39. pg_proc"><code class="structname">pg_proc</code></a>.oid</code></td><td>
OID of a handler function that is responsible for supplying information
about the access method
</td></tr><tr><td><code class="structfield">amtype</code></td><td><code class="type">char</code></td><td> </td><td>
Currently always <code class="literal">i</code> to indicate an index access
method; other values may be allowed in future
</td></tr></tbody></table></div></div><br class="table-break" /><div class="note"><h3 class="title">Note</h3><p>
Before <span class="productname">PostgreSQL</span> 9.6, <code class="structname">pg_am</code>
contained many additional columns representing properties of index access
methods. That data is now only directly visible at the C code level.
However, <code class="function">pg_index_column_has_property()</code> and related
functions have been added to allow SQL queries to inspect index access
method properties; see <a class="xref" href="functions-info.html#FUNCTIONS-INFO-CATALOG-TABLE" title="Table 9.63. System Catalog Information Functions">Table 9.63</a>.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="catalog-pg-aggregate.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-amop.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">52.2. <code class="structname">pg_aggregate</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 52.4. <code class="structname">pg_amop</code></td></tr></table></div></body></html>
