<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >pg_am</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.6.21 Documentation" HREF="index.html"><LINK REL="UP" TITLE="System Catalogs" HREF="catalogs.html"><LINK REL="PREVIOUS" TITLE="pg_aggregate" HREF="catalog-pg-aggregate.html"><LINK REL="NEXT" TITLE="pg_amop" HREF="catalog-pg-amop.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2021-02-27T18:26:08"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="4" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.6.21 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="pg_aggregate" HREF="catalog-pg-aggregate.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="catalogs.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 50. System Catalogs</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="pg_amop" HREF="catalog-pg-amop.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="CATALOG-PG-AM" >50.3. <TT CLASS="STRUCTNAME" >pg_am</TT ></A ></H1 ><P > The catalog <TT CLASS="STRUCTNAME" >pg_am</TT > 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 HREF="indexam.html" >Chapter 59</A >. </P ><DIV CLASS="TABLE" ><A NAME="AEN105712" ></A ><P ><B >Table 50-3. <TT CLASS="STRUCTNAME" >pg_am</TT > Columns</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><COL><THEAD ><TR ><TH >Name</TH ><TH >Type</TH ><TH >References</TH ><TH >Description</TH ></TR ></THEAD ><TBODY ><TR ><TD ><TT CLASS="STRUCTFIELD" >oid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD > </TD ><TD >Row identifier (hidden attribute; must be explicitly selected)</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >amname</TT ></TD ><TD ><TT CLASS="TYPE" >name</TT ></TD ><TD > </TD ><TD >Name of the access method</TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >amhandler</TT ></TD ><TD ><TT CLASS="TYPE" >regproc</TT ></TD ><TD ><TT CLASS="LITERAL" ><A HREF="catalog-pg-proc.html" ><TT CLASS="STRUCTNAME" >pg_proc</TT ></A >.oid</TT ></TD ><TD > OID of a handler function that is responsible for supplying information about the access method </TD ></TR ><TR ><TD ><TT CLASS="STRUCTFIELD" >amtype</TT ></TD ><TD ><TT CLASS="TYPE" >char</TT ></TD ><TD > </TD ><TD > Currently always <TT CLASS="LITERAL" >i</TT > to indicate an index access method; other values may be allowed in future </TD ></TR ></TBODY ></TABLE ></DIV ><DIV CLASS="NOTE" ><BLOCKQUOTE CLASS="NOTE" ><P ><B >Note: </B > Before <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > 9.6, <TT CLASS="STRUCTNAME" >pg_am</TT > 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 HREF="functions-info.html#FUNCTIONS-INFO-CATALOG-TABLE" >Table 9-62</A >. </P ></BLOCKQUOTE ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="catalog-pg-aggregate.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="catalog-pg-amop.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><TT CLASS="STRUCTNAME" >pg_aggregate</TT ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="catalogs.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><TT CLASS="STRUCTNAME" >pg_amop</TT ></TD ></TR ></TABLE ></DIV ></BODY ></HTML >