doc/src/sgml/ref/create_procedure.sgml

<!--
doc/src/sgml/ref/create_procedure.sgml
PostgreSQL documentation
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<refentry id="sql-createprocedure">
 <indexterm zone="sql-createprocedure">
  <primary>CREATE PROCEDURE</primary>
 </indexterm>

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

 <refnamediv>
  <refname>CREATE PROCEDURE</refname>
  <refpurpose>define a new procedure</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
CREATE [ OR REPLACE ] PROCEDURE
    <replaceable class="parameter">name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [ { DEFAULT | = } <replaceable class="parameter">default_expr</replaceable> ] [, ...] ] )
  { LANGUAGE <replaceable class="parameter">lang_name</replaceable>
    | TRANSFORM { FOR TYPE <replaceable class="parameter">type_name</replaceable> } [, ... ]
    | [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER
    | SET <replaceable class="parameter">configuration_parameter</replaceable> { TO <replaceable class="parameter">value</replaceable> | = <replaceable class="parameter">value</replaceable> | FROM CURRENT }
    | AS '<replaceable class="parameter">definition</replaceable>'
    | AS '<replaceable class="parameter">obj_file</replaceable>', '<replaceable class="parameter">link_symbol</replaceable>'
    | <replaceable class="parameter">sql_body</replaceable>
  } ...
</synopsis>
 </refsynopsisdiv>

 <refsect1 id="sql-createprocedure-description">
  <title>Description</title>

  <para>
   <command>CREATE PROCEDURE</command> defines a new procedure.
   <command>CREATE OR REPLACE PROCEDURE</command> will either create a
   new procedure, or replace an existing definition.
   To be able to define a procedure, the user must have the
   <literal>USAGE</literal> privilege on the language.
  </para>

  <para>
   If a schema name is included, then the procedure is created in the
   specified schema.  Otherwise it is created in the current schema.
   The name of the new procedure must not match any existing procedure or function
   with the same input argument types in the same schema.  However,
   procedures and functions of different argument types can share a name (this is
   called <firstterm>overloading</firstterm>).
  </para>

  <para>
   To replace the current definition of an existing procedure, use
   <command>CREATE OR REPLACE PROCEDURE</command>.  It is not possible
   to change the name or argument types of a procedure this way (if you
   tried, you would actually be creating a new, distinct procedure).
  </para>

  <para>
   When <command>CREATE OR REPLACE PROCEDURE</command> is used to replace an
   existing procedure, the ownership and permissions of the procedure
   do not change.  All other procedure properties are assigned the
   values specified or implied in the command.  You must own the procedure
   to replace it (this includes being a member of the owning role).
  </para>

  <para>
   The user that creates the procedure becomes the owner of the procedure.
  </para>

  <para>
   To be able to create a procedure, you must have <literal>USAGE</literal>
   privilege on the argument types.
  </para>

  <para>
   Refer to <xref linkend="xproc"/> for further information on writing
   procedures.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

   <variablelist>
    <varlistentry>
     <term><replaceable class="parameter">name</replaceable></term>

     <listitem>
      <para>
       The name (optionally schema-qualified) of the procedure to create.
      </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>.
      </para>
     </listitem>
    </varlistentry>

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

     <listitem>
      <para>
       The name of an argument.
      </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. The argument types can be base, composite,
       or domain types, or can reference the type of a table column.
      </para>
      <para>
       Depending on the implementation language it might also be allowed
       to specify <quote>pseudo-types</quote> such as <type>cstring</type>.
       Pseudo-types indicate that the actual argument type is either
       incompletely specified, or outside the set of ordinary SQL data types.
      </para>
      <para>
       The type of a column is referenced by writing
       <literal><replaceable
       class="parameter">table_name</replaceable>.<replaceable
       class="parameter">column_name</replaceable>%TYPE</literal>.
       Using this feature can sometimes help make a procedure independent of
       changes to the definition of a table.
      </para>
     </listitem>
    </varlistentry>

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

     <listitem>
      <para>
       An expression to be used as default value if the parameter is
       not specified.  The expression has to be coercible to the
       argument type of the parameter.
       All input parameters following a
       parameter with a default value must have default values as well.
      </para>
     </listitem>
    </varlistentry>

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

     <listitem>
      <para>
       The name of the language that the procedure is implemented in.
       It can be <literal>sql</literal>, <literal>c</literal>,
       <literal>internal</literal>, or the name of a user-defined
       procedural language, e.g., <literal>plpgsql</literal>.  The default is
       <literal>sql</literal> if <replaceable
       class="parameter">sql_body</replaceable> is specified.  Enclosing the
       name in single quotes is deprecated and requires matching case.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal>TRANSFORM { FOR TYPE <replaceable class="parameter">type_name</replaceable> } [, ... ] }</literal></term>

     <listitem>
      <para>
       Lists which transforms a call to the procedure should apply.  Transforms
       convert between SQL types and language-specific data types;
       see <xref linkend="sql-createtransform"/>.  Procedural language
       implementations usually have hardcoded knowledge of the built-in types,
       so those don't need to be listed here.  If a procedural language
       implementation does not know how to handle a type and no transform is
       supplied, it will fall back to a default behavior for converting data
       types, but this depends on the implementation.
      </para>
     </listitem>
    </varlistentry>

   <varlistentry>
    <term><literal><optional>EXTERNAL</optional> SECURITY INVOKER</literal></term>
    <term><literal><optional>EXTERNAL</optional> SECURITY DEFINER</literal></term>

    <listitem>
     <para><literal>SECURITY INVOKER</literal> indicates that the procedure
      is to be executed with the privileges of the user that calls it.
      That is the default.  <literal>SECURITY DEFINER</literal>
      specifies that the procedure is to be executed with the
      privileges of the user that owns it.
     </para>

     <para>
      The key word <literal>EXTERNAL</literal> is allowed for SQL
      conformance, but it is optional since, unlike in SQL, this feature
      applies to all procedures not only external ones.
     </para>

     <para>
      A <literal>SECURITY DEFINER</literal> procedure cannot execute
      transaction control statements (for example, <command>COMMIT</command>
      and <command>ROLLBACK</command>, depending on the language).
     </para>
    </listitem>
   </varlistentry>

    <varlistentry>
     <term><replaceable>configuration_parameter</replaceable></term>
     <term><replaceable>value</replaceable></term>
     <listitem>
      <para>
       The <literal>SET</literal> clause causes the specified configuration
       parameter to be set to the specified value when the procedure is
       entered, and then restored to its prior value when the procedure exits.
       <literal>SET FROM CURRENT</literal> saves the value of the parameter that
       is current when <command>CREATE PROCEDURE</command> is executed as the value
       to be applied when the procedure is entered.
      </para>

      <para>
       If a <literal>SET</literal> clause is attached to a procedure, then
       the effects of a <command>SET LOCAL</command> command executed inside the
       procedure for the same variable are restricted to the procedure: the
       configuration parameter's prior value is still restored at procedure exit.
       However, an ordinary
       <command>SET</command> command (without <literal>LOCAL</literal>) overrides the
       <literal>SET</literal> clause, much as it would do for a previous <command>SET
       LOCAL</command> command: the effects of such a command will persist after
       procedure exit, unless the current transaction is rolled back.
      </para>

      <para>
       If a <literal>SET</literal> clause is attached to a procedure, then
       that procedure cannot execute transaction control statements (for
       example, <command>COMMIT</command> and <command>ROLLBACK</command>,
       depending on the language).
      </para>

      <para>
       See <xref linkend="sql-set"/> and
       <xref linkend="runtime-config"/>
       for more information about allowed parameter names and values.
      </para>
     </listitem>
    </varlistentry>

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

     <listitem>
      <para>
       A string constant defining the procedure; the meaning depends on the
       language.  It can be an internal procedure name, the path to an
       object file, an SQL command, or text in a procedural language.
      </para>

      <para>
       It is often helpful to use dollar quoting (see <xref
       linkend="sql-syntax-dollar-quoting"/>) to write the procedure definition
       string, rather than the normal single quote syntax.  Without dollar
       quoting, any single quotes or backslashes in the procedure definition must
       be escaped by doubling them.
      </para>

     </listitem>
    </varlistentry>

    <varlistentry>
     <term><literal><replaceable class="parameter">obj_file</replaceable>, <replaceable class="parameter">link_symbol</replaceable></literal></term>

     <listitem>
      <para>
       This form of the <literal>AS</literal> clause is used for
       dynamically loadable C language procedures when the procedure name
       in the C language source code is not the same as the name of
       the SQL procedure. The string <replaceable
       class="parameter">obj_file</replaceable> is the name of the shared
       library file containing the compiled C procedure, and is interpreted
       as for the <link linkend="sql-load"><command>LOAD</command></link> command.  The string
       <replaceable class="parameter">link_symbol</replaceable> is the
       procedure's link symbol, that is, the name of the procedure in the C
       language source code.  If the link symbol is omitted, it is assumed
       to be the same as the name of the SQL procedure being defined.
      </para>

      <para>
       When repeated <command>CREATE PROCEDURE</command> calls refer to
       the same object file, the file is only loaded once per session.
       To unload and
       reload the file (perhaps during development), start a new session.
      </para>

     </listitem>
    </varlistentry>

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

     <listitem>
      <para>
       The body of a <literal>LANGUAGE SQL</literal> procedure.  This should
       be a block
<programlisting>
BEGIN ATOMIC
  <replaceable>statement</replaceable>;
  <replaceable>statement</replaceable>;
  ...
  <replaceable>statement</replaceable>;
END
</programlisting>
      </para>

      <para>
       This is similar to writing the text of the procedure body as a string
       constant (see <replaceable>definition</replaceable> above), but there
       are some differences: This form only works for <literal>LANGUAGE
       SQL</literal>, the string constant form works for all languages.  This
       form is parsed at procedure definition time, the string constant form is
       parsed at execution time; therefore this form cannot support
       polymorphic argument types and other constructs that are not resolvable
       at procedure definition time.  This form tracks dependencies between the
       procedure and objects used in the procedure body, so <literal>DROP
       ... CASCADE</literal> will work correctly, whereas the form using
       string literals may leave dangling procedures.  Finally, this form is
       more compatible with the SQL standard and other SQL implementations.
      </para>
     </listitem>
    </varlistentry>

   </variablelist>
 </refsect1>

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

  <para>
   See <xref linkend="sql-createfunction"/> for more details on function
   creation that also apply to procedures.
  </para>

  <para>
   Use <xref linkend="sql-call"/> to execute a procedure.
  </para>
 </refsect1>

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

  <para>
<programlisting>
CREATE PROCEDURE insert_data(a integer, b integer)
LANGUAGE SQL
AS $$
INSERT INTO tbl VALUES (a);
INSERT INTO tbl VALUES (b);
$$;
</programlisting>
   or
<programlisting>
CREATE PROCEDURE insert_data(a integer, b integer)
LANGUAGE SQL
BEGIN ATOMIC
  INSERT INTO tbl VALUES (a);
  INSERT INTO tbl VALUES (b);
END;
</programlisting>
   and call like this:
<programlisting>
CALL insert_data(1, 2);
</programlisting></para>
 </refsect1>

 <refsect1 id="sql-createprocedure-compat">
  <title>Compatibility</title>

  <para>
   A <command>CREATE PROCEDURE</command> command is defined in the SQL
   standard.  The <productname>PostgreSQL</productname> implementation can be
   used in a compatible way but has many extensions.  For details see also
   <xref linkend="sql-createfunction"/>.
  </para>
 </refsect1>


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

  <simplelist type="inline">
   <member><xref linkend="sql-alterprocedure"/></member>
   <member><xref linkend="sql-dropprocedure"/></member>
   <member><xref linkend="sql-call"/></member>
   <member><xref linkend="sql-createfunction"/></member>
  </simplelist>
 </refsect1>

</refentry>