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doc/src/sgml/ref/refresh_materialized_view.sgml
PostgreSQL documentation
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<refentry id="sql-refreshmaterializedview">
 <indexterm zone="sql-refreshmaterializedview">
  <primary>REFRESH MATERIALIZED VIEW</primary>
 </indexterm>

 <refmeta>
  <refentrytitle>REFRESH MATERIALIZED VIEW</refentrytitle>
  <manvolnum>7</manvolnum>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>REFRESH MATERIALIZED VIEW</refname>
  <refpurpose>replace the contents of a materialized view</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
REFRESH MATERIALIZED VIEW [ CONCURRENTLY ] <replaceable class="parameter">name</replaceable>
    [ WITH [ NO ] DATA ]
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>REFRESH MATERIALIZED VIEW</command> completely replaces the
   contents of a materialized view.  To execute this command you must be the
   owner of the materialized view.  The old contents are discarded.  If
   <literal>WITH DATA</literal> is specified (or defaults) the backing query
   is executed to provide the new data, and the materialized view is left in a
   scannable state.  If the view is an incrementally maintainable materialized
   view (IMMV) and was unpopulated, triggers for maintaining the view are
   created. Also, a unique index is created for IMMV if it is possible and the
   view doesn't have that yet.
   If <literal>WITH NO DATA</literal> is specified no new
   data is generated and the materialized view is left in an unscannable
   state.  If the view is IMMV, the triggers are dropped.
  </para>
  <para>
   <literal>CONCURRENTLY</literal> and <literal>WITH NO DATA</literal> may not
   be specified together.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><literal>CONCURRENTLY</literal></term>
    <listitem>
     <para>
      Refresh the materialized view without locking out concurrent selects on
      the materialized view.  Without this option a refresh which affects a
      lot of rows will tend to use fewer resources and complete more quickly,
      but could block other connections which are trying to read from the
      materialized view.  This option may be faster in cases where a small
      number of rows are affected.
     </para>
     <para>
      This option is only allowed if there is at least one
      <literal>UNIQUE</literal> index on the materialized view which uses only
      column names and includes all rows;  that is, it must not be an
      expression index or include a <literal>WHERE</literal> clause.
     </para>
     <para>
      This option may not be used when the materialized view is not already
      populated.
     </para>
     <para>
      Even with this option only one <literal>REFRESH</literal> at a time may
      run against any one materialized view.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of the materialized view to
      refresh.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   If there is an <literal>ORDER BY</literal> clause in the materialized
   view's defining query, the original contents of the materialized view
   will be ordered that way; but <command>REFRESH MATERIALIZED
   VIEW</command> does not guarantee to preserve that ordering.
  </para>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   This command will replace the contents of the materialized view called
   <literal>order_summary</literal> using the query from the materialized
   view's definition, and leave it in a scannable state:
<programlisting>
REFRESH MATERIALIZED VIEW order_summary;
</programlisting>
  </para>

  <para>
   This command will free storage associated with the materialized view
   <literal>annual_statistics_basis</literal> and leave it in an unscannable
   state:
<programlisting>
REFRESH MATERIALIZED VIEW annual_statistics_basis WITH NO DATA;
</programlisting></para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   <command>REFRESH MATERIALIZED VIEW</command> is a
   <productname>PostgreSQL</productname> extension.
  </para>
 </refsect1>

 <refsect1>
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="sql-creatematerializedview"/></member>
   <member><xref linkend="sql-altermaterializedview"/></member>
   <member><xref linkend="sql-dropmaterializedview"/></member>
  </simplelist>
 </refsect1>

</refentry>
