<type>bool</type>
      </para>
      <para>
       True if the extension can be installed by non-superusers
       with appropriate privileges
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relocatable</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>schema</structfield> <type>name</type>
      </para>
      <para>
       Name of the schema that the extension must be installed into,
       or <literal>NULL</literal> if partially or fully relocatable
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>requires</structfield> <type>name[]</type>
      </para>
      <para>
       Names of prerequisite extensions,
       or <literal>NULL</literal> if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>comment</structfield> <type>text</type>
      </para>
      <para>
       Comment string from the extension's control file
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   The <structname>pg_available_extension_versions</structname> view is
   read-only.
  </para>
 </sect1>

 <sect1 id="view-pg-backend-memory-contexts">
  <title><structname>pg_backend_memory_contexts</structname></title>

  <indexterm zone="view-pg-backend-memory-contexts">
   <primary>pg_backend_memory_contexts</primary>
  </indexterm>

  <para>
   The view <structname>pg_backend_memory_contexts</structname> displays all
   the memory contexts of the server process attached to the current session.
  </para>
  <para>
   <structname>pg_backend_memory_contexts</structname> contains one row
   for each memory context.
  </para>

  <table>
   <title><structname>pg_backend_memory_contexts</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>name</structfield> <type>text</type>
      </para>
      <para>
       Name of the memory context
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ident</structfield> <type>text</type>
      </para>
      <para>
       Identification information of the memory context. This field is truncated at 1024 bytes
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>type</structfield> <type>text</type>
      </para>
      <para>
       Type of the memory context
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>level</structfield> <type>int4</type>
      </para>
      <para>
       The 1-based level of the context in the memory context hierarchy. The
       level of a context also shows the position of that context in the
       <structfield>path</structfield> column.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>path</structfield> <type>int4[]</type>
      </para>
      <para>
       Array of transient numerical identifiers to describe the memory
       context hierarchy. The first element is for
       <literal>TopMemoryContext</literal>, subsequent elements contain
       intermediate parents and the final element contains the identifier for
       the current context.
      </para></entry>