doc/src/sgml/ref/drop_procedure.sgml - master - githubmirror/postgres

doc/src/sgml/ref/drop_procedure.sgml
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Peter Eisentraut
doc: Fix man page whitespace issues
07 апр 2022, 19:25
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<!--
doc/src/sgml/ref/drop_procedure.sgml
PostgreSQL documentation
-->

<refentry id="sql-dropprocedure">
 <indexterm zone="sql-dropprocedure">
  <primary>DROP PROCEDURE</primary>
 </indexterm>

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

 <refnamediv>
  <refname>DROP PROCEDURE</refname>
  <refpurpose>remove a procedure</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
DROP PROCEDURE [ 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 PROCEDURE</command> removes the definition of one or more
   existing procedures. To execute this command the user must be the
   owner of the procedure(s). The argument types to the
   procedure(s) usually must be specified, since several different procedures
   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 procedure 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 procedure.
     </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> (but see below).
     </para>
    </listitem>
   </varlistentry>

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

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

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

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

   <varlistentry>
    <term><literal>CASCADE</literal></term>
    <listitem>
     <para>
      Automatically drop objects that depend on the procedure,
      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 procedure if any objects depend on it.  This
      is the default.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1 id="sql-dropprocedure-notes">
  <title>Notes</title>

  <para>
   If there is only one procedure of the given name, the argument list
   can be omitted.  Omit the parentheses too in this case.
  </para>

  <para>
   In <productname>PostgreSQL</productname>, it's sufficient to list the
   input (including <literal>INOUT</literal>) arguments,
   because no two routines of the same name are allowed to share the same
   input-argument list.  Moreover, the <command>DROP</command> command
   will not actually check that you wrote the types
   of <literal>OUT</literal> arguments correctly; so any arguments that
   are explicitly marked <literal>OUT</literal> are just noise.  But
   writing them is recommendable for consistency with the
   corresponding <command>CREATE</command> command.
  </para>

  <para>
   For compatibility with the SQL standard, it is also allowed to write
   all the argument data types (including those of <literal>OUT</literal>
   arguments) without
   any <replaceable class="parameter">argmode</replaceable> markers.
   When this is done, the types of the procedure's <literal>OUT</literal>
   argument(s) <emphasis>will</emphasis> be verified against the command.
   This provision creates an ambiguity, in that when the argument list
   contains no <replaceable class="parameter">argmode</replaceable>
   markers, it's unclear which rule is intended.
   The <command>DROP</command> command will attempt the lookup both ways,
   and will throw an error if two different procedures are found.
   To avoid the risk of such ambiguity, it's recommendable to
   write <literal>IN</literal> markers explicitly rather than letting them
   be defaulted, thus forcing the
   traditional <productname>PostgreSQL</productname> interpretation to be
   used.
  </para>

  <para>
   The lookup rules just explained are also used by other commands that
   act on existing procedures, such as <command>ALTER PROCEDURE</command>
   and <command>COMMENT ON PROCEDURE</command>.
  </para>
 </refsect1>

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

  <para>
   If there is only one procedure <literal>do_db_maintenance</literal>,
   this command is sufficient to drop it:
<programlisting>
DROP PROCEDURE do_db_maintenance;
</programlisting>
  </para>

  <para>
   Given this procedure definition:
<programlisting>
CREATE PROCEDURE do_db_maintenance(IN target_schema text, OUT results text) ...
</programlisting>
   any one of these commands would work to drop it:
<programlisting>
DROP PROCEDURE do_db_maintenance(IN target_schema text, OUT results text);
DROP PROCEDURE do_db_maintenance(IN text, OUT text);
DROP PROCEDURE do_db_maintenance(IN text);
DROP PROCEDURE do_db_maintenance(text);
DROP PROCEDURE do_db_maintenance(text, text);  -- potentially ambiguous
</programlisting>
   However, the last example would be ambiguous if there is also, say,
<programlisting>
CREATE PROCEDURE do_db_maintenance(IN target_schema text, IN options text) ...
</programlisting></para>
 </refsect1>

 <refsect1 id="sql-dropprocedure-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 procedure to be dropped per command.</para>
    </listitem>
    <listitem>
     <para>The <literal>IF EXISTS</literal> option is an extension.</para>
    </listitem>
    <listitem>
     <para>The ability to specify argument modes and names is an
     extension, and the lookup rules differ when modes are given.</para>
    </listitem>
   </itemizedlist></para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="sql-createprocedure"/></member>
   <member><xref linkend="sql-alterprocedure"/></member>
   <member><xref linkend="sql-dropfunction"/></member>
   <member><xref linkend="sql-droproutine"/></member>
  </simplelist>
 </refsect1>

</refentry>