means that if a <application>PL/pgSQL</application> function produces a
       very large result set, performance might be poor: data will be
       written to disk to avoid memory exhaustion, but the function
       itself will not return until the entire result set has been
       generated.  A future version of <application>PL/pgSQL</application> might
       allow users to define set-returning functions
       that do not have this limitation.  Currently, the point at
       which data begins being written to disk is controlled by the
       <xref linkend="guc-work-mem"/>
       configuration variable.  Administrators who have sufficient
       memory to store larger result sets in memory should consider
       increasing this parameter.
      </para>
     </note>
    </sect3>
   </sect2>

   <sect2 id="plpgsql-statements-returning-procedure">
    <title>Returning from a Procedure</title>

    <para>
     A procedure does not have a return value.  A procedure can therefore end
     without a <command>RETURN</command> statement.  If you wish to use
     a <command>RETURN</command> statement to exit the code early, write
     just <command>RETURN</command> with no expression.
    </para>

    <para>
     If the procedure has output parameters, the final values of the output
     parameter variables will be returned to the caller.
    </para>
   </sect2>

   <sect2 id="plpgsql-statements-calling-procedure">
    <title>Calling a Procedure</title>

    <para>
     A <application>PL/pgSQL</application> function, procedure,
     or <command>DO</command> block can call a procedure
     using <command>CALL</command>.  Output parameters are handled
     differently from the way that <command>CALL</command> works in plain
     SQL.  Each <literal>OUT</literal> or <literal>INOUT</literal>
     parameter of the procedure must
     correspond to a variable in the <command>CALL</command> statement, and
     whatever the procedure returns is assigned back to that variable after
     it returns.  For example:
<programlisting>
CREATE PROCEDURE triple(INOUT x int)
LANGUAGE plpgsql
AS $$
BEGIN
    x := x * 3;
END;
$$;

DO $$
DECLARE myvar int := 5;
BEGIN
  CALL triple(myvar);
  RAISE NOTICE 'myvar = %', myvar;  -- prints 15
END;
$$;
</programlisting>
     The variable corresponding to an output parameter can be a simple
     variable or a field of a composite-type variable.  Currently,
     it cannot be an element of an array.
    </para>
   </sect2>

   <sect2 id="plpgsql-conditionals">
    <title>Conditionals</title>

    <para>
     <command>IF</command> and <command>CASE</command> statements let you execute
     alternative commands based on certain conditions.
     <application>PL/pgSQL</application> has three forms of <command>IF</command>:
    <itemizedlist>
     <listitem>
      <para><literal>IF ... THEN ... END IF</literal></para>
     </listitem>
     <listitem>
      <para><literal>IF ... THEN ... ELSE ... END IF</literal></para>
     </listitem>
     <listitem>
      <para><literal>IF ... THEN ... ELSIF ... THEN ... ELSE ... END IF</literal></para>
     </listitem>
    </itemizedlist>

    and two forms of <command>CASE</command>:
    <itemizedlist>
     <listitem>
      <para><literal>CASE ... WHEN ... THEN ... ELSE ... END CASE</literal></para>
     </listitem>
     <listitem>
      <para><literal>CASE WHEN ... THEN ... ELSE ... END CASE</literal></para>
     </listitem>
    </itemizedlist>
    </para>

    <sect3 id="plpgsql-conditionals-if-then">
     <title><literal>IF-THEN</literal></title>

<synopsis>
IF <replaceable>boolean-expression</replaceable> THEN
    <replaceable>statements</replaceable>
END IF;
</synopsis>

       <para>
        <literal>IF-THEN</literal> statements are the simplest form of
        <literal>IF</literal>. The statements between
        <literal>THEN</literal> and <literal>END IF</literal> will be
        executed if the condition is true. Otherwise, they are
        skipped.
       </para>