doc/src/sgml/ref/create_access_method.sgml

   1 <!--
   2 doc/src/sgml/ref/create_access_method.sgml
   3 PostgreSQL documentation
   4 -->
   5
   6 <refentry id="sql-create-access-method">
   7  <indexterm zone="sql-create-access-method">
   8   <primary>CREATE ACCESS METHOD</primary>
   9  </indexterm>
  10
  11  <refmeta>
  12   <refentrytitle>CREATE ACCESS METHOD</refentrytitle>
  13   <manvolnum>7</manvolnum>
  14   <refmiscinfo>SQL - Language Statements</refmiscinfo>
  15  </refmeta>
  16
  17  <refnamediv>
  18   <refname>CREATE ACCESS METHOD</refname>
  19   <refpurpose>define a new access method</refpurpose>
  20  </refnamediv>
  21
  22  <refsynopsisdiv>
  23 <synopsis>
  24 CREATE ACCESS METHOD <replaceable class="parameter">name</replaceable>
  25     TYPE <replaceable class="parameter">access_method_type</replaceable>
  26     HANDLER <replaceable class="parameter">handler_function</replaceable>
  27 </synopsis>
  28  </refsynopsisdiv>
  29
  30  <refsect1>
  31   <title>Description</title>
  32
  33   <para>
  34    <command>CREATE ACCESS METHOD</command> creates a new access method.
  35   </para>
  36
  37   <para>
  38    The access method name must be unique within the database.
  39   </para>
  40
  41   <para>
  42    Only superusers can define new access methods.
  43   </para>
  44  </refsect1>
  45
  46  <refsect1>
  47   <title>Parameters</title>
  48
  49   <variablelist>
  50    <varlistentry>
  51     <term><replaceable class="parameter">name</replaceable></term>
  52     <listitem>
  53      <para>
  54       The name of the access method to be created.
  55      </para>
  56     </listitem>
  57    </varlistentry>
  58
  59    <varlistentry>
  60     <term><replaceable class="parameter">access_method_type</replaceable></term>
  61     <listitem>
  62      <para>
  63       This clause specifies the type of access method to define.
  64       Only <literal>TABLE</literal> and <literal>INDEX</literal>
  65       are supported at present.
  66      </para>
  67     </listitem>
  68    </varlistentry>
  69
  70    <varlistentry>
  71     <term><replaceable class="parameter">handler_function</replaceable></term>
  72     <listitem>
  73      <para>
  74       <replaceable class="parameter">handler_function</replaceable> is the
  75       name (possibly schema-qualified) of a previously registered function
  76       that represents the access method.  The handler function must be
  77       declared to take a single argument of type <type>internal</type>,
  78       and its return type depends on the type of access method;
  79       for <literal>TABLE</literal> access methods, it must
  80       be <type>table_am_handler</type> and for <literal>INDEX</literal>
  81       access methods, it must be <type>index_am_handler</type>.
  82       The C-level API that the handler function must implement varies
  83       depending on the type of access method. The table access method API
  84       is described in <xref linkend="tableam"/> and the index access method
  85       API is described in <xref linkend="indexam"/>.
  86      </para>
  87     </listitem>
  88    </varlistentry>
  89   </variablelist>
  90  </refsect1>
  91
  92  <refsect1>
  93   <title>Examples</title>
  94
  95   <para>
  96    Create an index access method <literal>heptree</literal> with
  97    handler function <literal>heptree_handler</literal>:
  98 <programlisting>
  99 CREATE ACCESS METHOD heptree TYPE INDEX HANDLER heptree_handler;
 100 </programlisting></para>
 101  </refsect1>
 102
 103  <refsect1>
 104   <title>Compatibility</title>
 105
 106   <para>
 107    <command>CREATE ACCESS METHOD</command> is a
 108    <productname>PostgreSQL</productname> extension.
 109   </para>
 110  </refsect1>
 111
 112  <refsect1>
 113   <title>See Also</title>
 114
 115   <simplelist type="inline">
 116    <member><xref linkend="sql-drop-access-method"/></member>
 117    <member><xref linkend="sql-createopclass"/></member>
 118    <member><xref linkend="sql-createopfamily"/></member>
 119   </simplelist>
 120  </refsect1>
 121
 122 </refentry>