<!--
doc/src/sgml/ref/drop_function.sgml
PostgreSQL documentation
-->

<refentry id="sql-dropfunction">
 <indexterm zone="sql-dropfunction">
  <primary>DROP FUNCTION</primary>
 </indexterm>

 <refmeta>
  <refentrytitle>DROP FUNCTION</refentrytitle>
  <manvolnum>7</manvolnum>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>DROP FUNCTION</refname>
  <refpurpose>remove a function</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
DROP FUNCTION [ IF EXISTS ] <replaceable class="parameter">name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ] [, ...]
    [ CASCADE | RESTRICT ]
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>DROP FUNCTION</command> removes the definition of an existing
   function. To execute this command the user must be the
   owner of the function. The argument types to the
   function must be specified, since several different functions
   can exist with the same name and different argument lists.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

  <variablelist>
    <varlistentry>
    <term><literal>IF EXISTS</literal></term>
    <listitem>
     <para>
      Do not throw an error if the function does not exist. A notice is issued
      in this case.
     </para>
    </listitem>
   </varlistentry>

  <varlistentry>
    <term><replaceable class="parameter">name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an existing function.  If no
      argument list is specified, the name must be unique in its schema.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argmode</replaceable></term>

    <listitem>
     <para>
      The mode of an argument: <literal>IN</literal>, <literal>OUT</literal>,
      <literal>INOUT</literal>, or <literal>VARIADIC</literal>.
      If omitted, the default is <literal>IN</literal>.
      Note that <command>DROP FUNCTION</command> does not actually pay
      any attention to <literal>OUT</literal> arguments, since only the input
      arguments are needed to determine the function's identity.
      So it is sufficient to list the <literal>IN</literal>, <literal>INOUT</literal>,
      and <literal>VARIADIC</literal> arguments.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argname</replaceable></term>

    <listitem>
     <para>
      The name of an argument.
      Note that <command>DROP FUNCTION</command> does not actually pay
      any attention to argument names, since only the argument data
      types are needed to determine the function's identity.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">argtype</replaceable></term>

    <listitem>
     <para>
      The data type(s) of the function's arguments (optionally
      schema-qualified), if any.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>CASCADE</literal></term>
    <listitem>
     <para>
      Automatically drop objects that depend on the function (such as
      operators or triggers),
      and in turn all objects that depend on those objects
      (see <xref linkend="ddl-depend"/>).
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>RESTRICT</literal></term>
    <listitem>
     <para>
      Refuse to drop the function if any objects depend on it.  This
      is the default.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1 id="sql-dropfunction-examples">
  <title>Examples</title>

  <para>
   This command removes the square root function:

<programlisting>
DROP FUNCTION sqrt(integer);
</programlisting></para>

  <para>
   Drop multiple functions in one command:
<programlisting>
DROP FUNCTION sqrt(integer), sqrt(bigint);
</programlisting></para>

  <para>
   If the function name is unique in its schema, it can be referred to without
   an argument list:
<programlisting>
DROP FUNCTION update_employee_salaries;
</programlisting>
   Note that this is different from
<programlisting>
DROP FUNCTION update_employee_salaries();
</programlisting>
   which refers to a function with zero arguments, whereas the first variant
   can refer to a function with any number of arguments, including zero, as
   long as the name is unique.
  </para>
 </refsect1>

 <refsect1 id="sql-dropfunction-compatibility">
  <title>Compatibility</title>

  <para>
   This command conforms to the SQL standard, with
   these <productname>PostgreSQL</productname> extensions:
   <itemizedlist>
    <listitem>
     <para>The standard only allows one function to be dropped per command.</para>
    </listitem>
    <listitem>
     <para>The <literal>IF EXISTS</literal> option</para>
    </listitem>
    <listitem>
     <para>The ability to specify argument modes and names</para>
    </listitem>
   </itemizedlist>
  </para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="sql-createfunction"/></member>
   <member><xref linkend="sql-alterfunction"/></member>
  </simplelist>
 </refsect1>

</refentry>
