doc/src/sgml/ref/refresh_materialized_view.sgml

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   2 doc/src/sgml/ref/refresh_materialized_view.sgml
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   5
   6 <refentry id="sql-refreshmaterializedview">
   7  <indexterm zone="sql-refreshmaterializedview">
   8   <primary>REFRESH MATERIALIZED VIEW</primary>
   9  </indexterm>
  10
  11  <refmeta>
  12   <refentrytitle>REFRESH MATERIALIZED VIEW</refentrytitle>
  13   <manvolnum>7</manvolnum>
  14   <refmiscinfo>SQL - Language Statements</refmiscinfo>
  15  </refmeta>
  16
  17  <refnamediv>
  18   <refname>REFRESH MATERIALIZED VIEW</refname>
  19   <refpurpose>replace the contents of a materialized view</refpurpose>
  20  </refnamediv>
  21
  22  <refsynopsisdiv>
  23 <synopsis>
  24 REFRESH MATERIALIZED VIEW [ CONCURRENTLY ] <replaceable class="parameter">name</replaceable>
  25     [ WITH [ NO ] DATA ]
  26 </synopsis>
  27  </refsynopsisdiv>
  28
  29  <refsect1>
  30   <title>Description</title>
  31
  32   <para>
  33    <command>REFRESH MATERIALIZED VIEW</command> completely replaces the
  34    contents of a materialized view.  To execute this command you must have the
  35    <literal>MAINTAIN</literal>
  36    privilege on the materialized view.  The old contents are discarded.  If
  37    <literal>WITH DATA</literal> is specified (or defaults) the backing query
  38    is executed to provide the new data, and the materialized view is left in a
  39    scannable state.  If <literal>WITH NO DATA</literal> is specified no new
  40    data is generated and the materialized view is left in an unscannable
  41    state.
  42   </para>
  43   <para>
  44    <literal>CONCURRENTLY</literal> and <literal>WITH NO DATA</literal> may not
  45    be specified together.
  46   </para>
  47  </refsect1>
  48
  49  <refsect1>
  50   <title>Parameters</title>
  51
  52   <variablelist>
  53    <varlistentry>
  54     <term><literal>CONCURRENTLY</literal></term>
  55     <listitem>
  56      <para>
  57       Refresh the materialized view without locking out concurrent selects on
  58       the materialized view.  Without this option a refresh which affects a
  59       lot of rows will tend to use fewer resources and complete more quickly,
  60       but could block other connections which are trying to read from the
  61       materialized view.  This option may be faster in cases where a small
  62       number of rows are affected.
  63      </para>
  64      <para>
  65       This option is only allowed if there is at least one
  66       <literal>UNIQUE</literal> index on the materialized view which uses only
  67       column names and includes all rows;  that is, it must not be an
  68       expression index or include a <literal>WHERE</literal> clause.
  69      </para>
  70      <para>
  71       This option can only be used when the materialized view is already
  72       populated.
  73      </para>
  74      <para>
  75       Even with this option only one <literal>REFRESH</literal> at a time may
  76       run against any one materialized view.
  77      </para>
  78     </listitem>
  79    </varlistentry>
  80
  81    <varlistentry>
  82     <term><replaceable class="parameter">name</replaceable></term>
  83     <listitem>
  84      <para>
  85       The name (optionally schema-qualified) of the materialized view to
  86       refresh.
  87      </para>
  88     </listitem>
  89    </varlistentry>
  90   </variablelist>
  91  </refsect1>
  92
  93  <refsect1>
  94   <title>Notes</title>
  95
  96   <para>
  97    If there is an <literal>ORDER BY</literal> clause in the materialized
  98    view's defining query, the original contents of the materialized view
  99    will be ordered that way; but <command>REFRESH MATERIALIZED
 100    VIEW</command> does not guarantee to preserve that ordering.
 101   </para>
 102
 103   <para>
 104    While <command>REFRESH MATERIALIZED VIEW</command> is running, the <xref
 105    linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
 106    pg_temp</literal>.
 107   </para>
 108  </refsect1>
 109
 110  <refsect1>
 111   <title>Examples</title>
 112
 113   <para>
 114    This command will replace the contents of the materialized view called
 115    <literal>order_summary</literal> using the query from the materialized
 116    view's definition, and leave it in a scannable state:
 117 <programlisting>
 118 REFRESH MATERIALIZED VIEW order_summary;
 119 </programlisting>
 120   </para>
 121
 122   <para>
 123    This command will free storage associated with the materialized view
 124    <literal>annual_statistics_basis</literal> and leave it in an unscannable
 125    state:
 126 <programlisting>
 127 REFRESH MATERIALIZED VIEW annual_statistics_basis WITH NO DATA;
 128 </programlisting></para>
 129  </refsect1>
 130
 131  <refsect1>
 132   <title>Compatibility</title>
 133
 134   <para>
 135    <command>REFRESH MATERIALIZED VIEW</command> is a
 136    <productname>PostgreSQL</productname> extension.
 137   </para>
 138  </refsect1>
 139
 140  <refsect1>
 141   <title>See Also</title>
 142
 143   <simplelist type="inline">
 144    <member><xref linkend="sql-creatematerializedview"/></member>
 145    <member><xref linkend="sql-altermaterializedview"/></member>
 146    <member><xref linkend="sql-dropmaterializedview"/></member>
 147   </simplelist>
 148  </refsect1>
 149
 150 </refentry>