134 lines
3.5 KiB
Plaintext
134 lines
3.5 KiB
Plaintext
<!--
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doc/src/sgml/ref/call.sgml
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PostgreSQL documentation
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-->
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<refentry id="sql-call">
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<indexterm zone="sql-call">
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<primary>CALL</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>CALL</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>CALL</refname>
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<refpurpose>invoke a procedure</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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CALL <replaceable class="parameter">name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> ] [, ...] )
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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>CALL</command> executes a procedure.
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</para>
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<para>
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If the procedure has any output parameters, then a result row will be
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returned, containing the values of those parameters.
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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><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 procedure.
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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">argument</replaceable></term>
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<listitem>
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<para>
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An argument expression for the procedure call.
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</para>
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<para>
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Arguments can include parameter names, using the syntax
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<literal><replaceable class="parameter">name</replaceable> => <replaceable class="parameter">value</replaceable></literal>.
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This works the same as in ordinary function calls; see
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<xref linkend="sql-syntax-calling-funcs"/> for details.
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</para>
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<para>
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Arguments must be supplied for all procedure parameters that lack
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defaults, including <literal>OUT</literal> parameters. However,
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arguments matching <literal>OUT</literal> parameters are not evaluated,
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so it's customary to just write <literal>NULL</literal> for them.
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(Writing something else for an <literal>OUT</literal> parameter
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might cause compatibility problems with
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future <productname>PostgreSQL</productname> versions.)
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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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The user must have <literal>EXECUTE</literal> privilege on the procedure in
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order to be allowed to invoke it.
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</para>
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<para>
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To call a function (not a procedure), use <command>SELECT</command> instead.
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</para>
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<para>
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If <command>CALL</command> is executed in a transaction block, then the
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called procedure cannot execute transaction control statements.
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Transaction control statements are only allowed if <command>CALL</command>
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is executed in its own transaction.
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</para>
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<para>
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<application>PL/pgSQL</application> handles output parameters
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in <command>CALL</command> commands differently;
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see <xref linkend="plpgsql-statements-calling-procedure"/>.
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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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<programlisting>
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CALL do_db_maintenance();
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</programlisting>
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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>CALL</command> conforms to the SQL standard,
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except for the handling of output parameters. The standard
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says that users should write variables to receive the values
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of output parameters.
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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-createprocedure"/></member>
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</simplelist>
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</refsect1>
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</refentry>
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