manager.
  </para>

  <para>
   Locking the regular and/or predicate lock manager could have some
   impact on database performance if this view is very frequently accessed.
   The locks are held only for the minimum amount of time necessary to
   obtain data from the lock managers, but this does not completely eliminate
   the possibility of a performance impact.
  </para>

 </sect1>

 <sect1 id="view-pg-matviews">
  <title><structname>pg_matviews</structname></title>

  <indexterm zone="view-pg-matviews">
   <primary>pg_matviews</primary>
  </indexterm>

  <indexterm zone="view-pg-matviews">
   <primary>materialized views</primary>
  </indexterm>

  <para>
   The view <structname>pg_matviews</structname> provides access to
   useful information about each materialized view in the database.
  </para>

  <table>
   <title><structname>pg_matviews</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>schemaname</structfield> <type>name</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>nspname</structfield>)
      </para>
      <para>
       Name of schema containing materialized view
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>matviewname</structfield> <type>name</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>relname</structfield>)
      </para>
      <para>
       Name of materialized view
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>matviewowner</structfield> <type>name</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>rolname</structfield>)
      </para>
      <para>
       Name of materialized view's owner
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tablespace</structfield> <type>name</type>
       (references <link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.<structfield>spcname</structfield>)
      </para>
      <para>
       Name of tablespace containing materialized view (null if default for database)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>hasindexes</structfield> <type>bool</type>
      </para>
      <para>
       True if materialized view has (or recently had) any indexes
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ispopulated</structfield> <type>bool</type>
      </para>
      <para>
       True if materialized view is currently populated
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>definition</structfield> <type>text</type>
      </para>
      <para>
       Materialized view definition (a reconstructed <xref linkend="sql-select"/> query)
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>

 <sect1 id="view-pg-policies">
  <title><structname>pg_policies</structname></title>

  <indexterm zone="view-pg-policies">
   <primary>pg_policies</primary>
  </indexterm>

  <para>
   The view <structname>pg_policies</structname> provides access to
   useful information about each row-level security policy in the database.
  </para>

  <table>
   <title><structname>pg_policies</structname> Columns</title>