146 lines
4.3 KiB
Plaintext
146 lines
4.3 KiB
Plaintext
<!--
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doc/src/sgml/ref/refresh_materialized_view.sgml
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PostgreSQL documentation
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-->
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<refentry id="sql-refreshmaterializedview">
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<indexterm zone="sql-refreshmaterializedview">
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<primary>REFRESH MATERIALIZED VIEW</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>REFRESH MATERIALIZED VIEW</refentrytitle>
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<manvolnum>7</manvolnum>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>REFRESH MATERIALIZED VIEW</refname>
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<refpurpose>replace the contents of a materialized view</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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REFRESH MATERIALIZED VIEW [ CONCURRENTLY ] <replaceable class="parameter">name</replaceable>
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[ WITH [ NO ] DATA ]
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>REFRESH MATERIALIZED VIEW</command> completely replaces the
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contents of a materialized view. To execute this command you must be the
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owner of the materialized view. The old contents are discarded. If
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<literal>WITH DATA</literal> is specified (or defaults) the backing query
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is executed to provide the new data, and the materialized view is left in a
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scannable state. If <literal>WITH NO DATA</literal> is specified no new
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data is generated and the materialized view is left in an unscannable
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state.
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</para>
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<para>
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<literal>CONCURRENTLY</literal> and <literal>WITH NO DATA</literal> may not
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be specified together.
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</para>
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</refsect1>
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<refsect1>
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<title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><literal>CONCURRENTLY</literal></term>
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<listitem>
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<para>
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Refresh the materialized view without locking out concurrent selects on
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the materialized view. Without this option a refresh which affects a
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lot of rows will tend to use fewer resources and complete more quickly,
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but could block other connections which are trying to read from the
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materialized view. This option may be faster in cases where a small
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number of rows are affected.
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</para>
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<para>
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This option is only allowed if there is at least one
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<literal>UNIQUE</literal> index on the materialized view which uses only
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column names and includes all rows; that is, it must not be an
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expression index or include a <literal>WHERE</literal> clause.
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</para>
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<para>
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This option may not be used when the materialized view is not already
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populated.
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</para>
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<para>
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Even with this option only one <literal>REFRESH</literal> at a time may
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run against any one materialized view.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">name</replaceable></term>
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<listitem>
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<para>
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The name (optionally schema-qualified) of the materialized view to
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refresh.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>
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While the default index for future
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<xref linkend="sql-cluster"/>
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operations is retained, <command>REFRESH MATERIALIZED VIEW</command> does not
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order the generated rows based on this property. If you want the data
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to be ordered upon generation, you must use an <literal>ORDER BY</literal>
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clause in the backing query.
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</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>
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This command will replace the contents of the materialized view called
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<literal>order_summary</literal> using the query from the materialized
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view's definition, and leave it in a scannable state:
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<programlisting>
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REFRESH MATERIALIZED VIEW order_summary;
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</programlisting>
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</para>
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<para>
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This command will free storage associated with the materialized view
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<literal>annual_statistics_basis</literal> and leave it in an unscannable
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state:
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<programlisting>
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REFRESH MATERIALIZED VIEW annual_statistics_basis WITH NO DATA;
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</programlisting></para>
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</refsect1>
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<refsect1>
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<title>Compatibility</title>
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<para>
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<command>REFRESH MATERIALIZED VIEW</command> is a
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<productname>PostgreSQL</productname> extension.
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</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="sql-creatematerializedview"/></member>
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<member><xref linkend="sql-altermaterializedview"/></member>
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<member><xref linkend="sql-dropmaterializedview"/></member>
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</simplelist>
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</refsect1>
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</refentry>
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