<structfield>evttags</structfield> <type>text[]</type>
      </para>
      <para>
       Command tags for which this trigger will fire.  If NULL, the firing
       of this trigger is not restricted on the basis of the command tag.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-extension">
  <title><structname>pg_extension</structname></title>

  <indexterm zone="catalog-pg-extension">
   <primary>pg_extension</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_extension</structname> stores information
   about the installed extensions.  See <xref linkend="extend-extensions"/>
   for details about extensions.
  </para>

  <table>
   <title><structname>pg_extension</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extname</structfield> <type>name</type>
      </para>
      <para>
       Name of the extension
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the extension
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Schema containing the extension's exported objects
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extrelocatable</structfield> <type>bool</type>
      </para>
      <para>
       True if extension can be relocated to another schema
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extversion</structfield> <type>text</type>
      </para>
      <para>
       Version name for the extension
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extconfig</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Array of <type>regclass</type> OIDs for the extension's configuration
       table(s), or <literal>NULL</literal> if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extcondition</structfield> <type>text[]</type>
      </para>
      <para>
       Array of <literal>WHERE</literal>-clause filter conditions for the
       extension's configuration table(s), or <literal>NULL</literal> if none
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   Note that unlike most catalogs with a <quote>namespace</quote> column,
   <structfield>extnamespace</structfield> is not meant to imply
   that the extension belongs to that schema.  Extension names are never
   schema-qualified.  Rather, <structfield>extnamespace</structfield>
   indicates the schema that contains most or all of the extension's
   objects.  If <structfield>extrelocatable</structfield>