1999-07-22 17:09:15 +02:00
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<!--
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2000-07-22 06:30:27 +02:00
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_function.sgml,v 1.15 2000/07/22 04:30:27 momjian Exp $
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1999-07-22 17:09:15 +02:00
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Postgres documentation
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-->
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1999-06-14 09:37:05 +02:00
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<refentry id="SQL-CREATEFUNCTION">
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<refmeta>
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1999-07-22 17:09:15 +02:00
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<refentrytitle id="sql-createfunction-title">
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1998-05-13 07:34:00 +02:00
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CREATE FUNCTION
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1999-06-14 09:37:05 +02:00
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</refentrytitle>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>
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1998-05-13 07:34:00 +02:00
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CREATE FUNCTION
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1999-06-14 09:37:05 +02:00
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</refname>
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<refpurpose>
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1998-05-13 07:34:00 +02:00
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Defines a new function
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1999-06-14 09:37:05 +02:00
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</refpurpose>
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1998-12-29 03:24:47 +01:00
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</refnamediv>
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1999-06-14 09:37:05 +02:00
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<refsynopsisdiv>
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<refsynopsisdivinfo>
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2000-03-27 19:14:43 +02:00
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<date>2000-03-25</date>
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1999-06-14 09:37:05 +02:00
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</refsynopsisdivinfo>
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<synopsis>
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1998-09-16 16:43:12 +02:00
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CREATE FUNCTION <replaceable class="parameter">name</replaceable> ( [ <replaceable class="parameter">ftype</replaceable> [, ...] ] )
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RETURNS <replaceable class="parameter">rtype</replaceable>
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
AS <replaceable class="parameter">definition</replaceable>
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1998-09-16 16:43:12 +02:00
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LANGUAGE '<replaceable class="parameter">langname</replaceable>'
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2000-03-27 19:14:43 +02:00
|
|
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[ WITH ( <replaceable class="parameter">attribute</replaceable> [, ...] ) ]
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
CREATE FUNCTION <replaceable class="parameter">name</replaceable> ( [ <replaceable class="parameter">ftype</replaceable> [, ...] ] )
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RETURNS <replaceable class="parameter">rtype</replaceable>
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AS <replaceable class="parameter">obj_file</replaceable> , <replaceable class="parameter">link_symbol</replaceable>
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1999-10-02 23:27:49 +02:00
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LANGUAGE 'C'
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2000-03-27 19:14:43 +02:00
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[ WITH ( <replaceable class="parameter">attribute</replaceable> [, ...] ) ]
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1999-06-14 09:37:05 +02:00
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</synopsis>
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1998-05-13 07:34:00 +02:00
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1999-06-14 09:37:05 +02:00
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<refsect2 id="R2-SQL-CREATEFUNCTION-1">
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<refsect2info>
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2000-03-27 19:14:43 +02:00
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<date>2000-03-25</date>
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1999-06-14 09:37:05 +02:00
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</refsect2info>
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<title>
|
1998-05-13 07:34:00 +02:00
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Inputs
|
1999-06-14 09:37:05 +02:00
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</title>
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<para>
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1999-07-06 19:16:42 +02:00
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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 of a function to create.
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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">ftype</replaceable></term>
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<listitem>
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<para>
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The data type of function arguments.
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1999-07-22 17:09:15 +02:00
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The input types may be base or complex types, or
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<firstterm>opaque</firstterm>.
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<literal>opaque</literal> indicates that the function
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accepts arguments of an invalid type such as <type>char *</type>.
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1999-07-06 19:16:42 +02:00
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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">rtype</replaceable></term>
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<listitem>
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<para>
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The return data type.
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1999-07-22 17:09:15 +02:00
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The output type may be specified as a base type, complex type,
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<literal>setof <replaceable class="parameter">type</replaceable></literal>,
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or <literal>opaque</literal>.
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The <literal>setof</literal>
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modifier indicates that the function will return a set of items,
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rather than a single item.
|
1999-07-06 19:16:42 +02:00
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</para>
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</listitem>
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</varlistentry>
|
1999-10-02 23:27:49 +02:00
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<varlistentry>
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<term><replaceable class="parameter">attribute</replaceable></term>
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<listitem>
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<para>
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An optional piece of information about the function, used for
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optimization. The only attribute currently supported is
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<literal>iscachable</literal>.
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<literal>iscachable</literal> indicates that the function always
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returns the same result when given the same input values (i.e.,
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it does not do database lookups or otherwise use information not
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|
directly present in its parameter list). The optimizer uses
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<literal>iscachable</literal> to know whether it is safe to
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pre-evaluate a call of the function.
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</para>
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</listitem>
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</varlistentry>
|
1999-07-06 19:16:42 +02:00
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<varlistentry>
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<term><replaceable class="parameter">definition</replaceable></term>
|
1999-06-14 09:37:05 +02:00
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<listitem>
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<para>
|
1999-05-20 04:57:15 +02:00
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A string defining the function; the meaning depends on the language.
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It may be an internal function name, the path to an object file,
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an SQL query, or text in a procedural language.
|
1999-06-14 09:37:05 +02:00
|
|
|
</para>
|
|
|
|
</listitem>
|
|
|
|
</varlistentry>
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
<varlistentry>
|
|
|
|
<term><replaceable class="parameter">obj_file</replaceable> , <replaceable class="parameter">link_symbol</replaceable></term>
|
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|
<listitem>
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<para>
|
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|
This form of the <command>AS</command> clause is used for
|
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|
dynamically-linked, C language functions when the function name in
|
|
|
|
the C language source code is not the same as the name of the SQL
|
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|
|
function. The string <replaceable
|
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class="parameter">obj_file</replaceable> is the name of the file
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|
|
containing the dynamically loadable object, and <replaceable
|
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|
class="parameter">link_symbol</replaceable>, is the object's link
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|
|
symbol which is the same as the name of the function in the C
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|
language source code.
|
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</para>
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</listitem>
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</varlistentry>
|
1999-06-14 09:37:05 +02:00
|
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|
<varlistentry>
|
1999-07-06 19:16:42 +02:00
|
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<term><replaceable class="parameter">langname</replaceable></term>
|
1999-06-14 09:37:05 +02:00
|
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|
<listitem>
|
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|
<para>
|
1998-12-29 03:24:47 +01:00
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|
may be '<literal>C</literal>', '<literal>sql</literal>',
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'<literal>internal</literal>'
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or '<replaceable class="parameter">plname</replaceable>',
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|
|
where '<replaceable class="parameter">plname</replaceable>'
|
1999-10-02 23:27:49 +02:00
|
|
|
is the name of a created procedural language. See
|
1999-07-22 17:09:15 +02:00
|
|
|
<xref linkend="sql-createlanguage-title" endterm="sql-createlanguage-title">
|
|
|
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for details.
|
1999-06-14 09:37:05 +02:00
|
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|
</para>
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|
</listitem>
|
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</varlistentry>
|
1998-12-29 03:24:47 +01:00
|
|
|
</variablelist>
|
|
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|
</para>
|
1999-06-14 09:37:05 +02:00
|
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|
</refsect2>
|
1999-07-06 19:16:42 +02:00
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1999-06-14 09:37:05 +02:00
|
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|
<refsect2 id="R2-SQL-CREATEFUNCTION-2">
|
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|
|
<refsect2info>
|
2000-03-27 19:14:43 +02:00
|
|
|
<date>2000-03-25</date>
|
1999-06-14 09:37:05 +02:00
|
|
|
</refsect2info>
|
|
|
|
<title>
|
1998-05-13 07:34:00 +02:00
|
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|
Outputs
|
1999-06-14 09:37:05 +02:00
|
|
|
</title>
|
|
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<para>
|
1999-07-06 19:16:42 +02:00
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1999-06-14 09:37:05 +02:00
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<variablelist>
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<varlistentry>
|
1999-07-06 19:16:42 +02:00
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<term><computeroutput>
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CREATE
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</computeroutput></term>
|
1999-06-14 09:37:05 +02:00
|
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<listitem>
|
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<para>
|
1998-12-29 03:24:47 +01:00
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|
This is returned if the command completes successfully.
|
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|
</para>
|
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</listitem>
|
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</varlistentry>
|
1999-06-14 09:37:05 +02:00
|
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|
</variablelist>
|
1998-12-29 03:24:47 +01:00
|
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</para>
|
1999-06-14 09:37:05 +02:00
|
|
|
</refsect2>
|
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</refsynopsisdiv>
|
1999-07-06 19:16:42 +02:00
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1999-06-14 09:37:05 +02:00
|
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|
<refsect1 id="R1-SQL-CREATEFUNCTION-1">
|
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<refsect1info>
|
2000-03-27 19:14:43 +02:00
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<date>2000-03-25</date>
|
1999-06-14 09:37:05 +02:00
|
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</refsect1info>
|
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<title>
|
1998-05-13 07:34:00 +02:00
|
|
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Description
|
1999-06-14 09:37:05 +02:00
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|
</title>
|
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<para>
|
1998-09-16 16:43:12 +02:00
|
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|
<command>CREATE FUNCTION</command> allows a
|
1998-12-29 03:24:47 +01:00
|
|
|
<productname>Postgres</productname> user
|
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|
|
to register a function
|
2000-03-27 19:14:43 +02:00
|
|
|
with a database. Subsequently, this user is considered the
|
1998-05-13 07:34:00 +02:00
|
|
|
owner of the function.
|
1999-06-14 09:37:05 +02:00
|
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|
</para>
|
1998-05-13 07:34:00 +02:00
|
|
|
|
1999-06-14 09:37:05 +02:00
|
|
|
<refsect2 id="R2-SQL-CREATEFUNCTION-3">
|
|
|
|
<refsect2info>
|
2000-03-27 19:14:43 +02:00
|
|
|
<date>2000-03-25</date>
|
1999-06-14 09:37:05 +02:00
|
|
|
</refsect2info>
|
|
|
|
<title>
|
1998-05-13 07:34:00 +02:00
|
|
|
Notes
|
1999-06-14 09:37:05 +02:00
|
|
|
</title>
|
2000-03-27 19:14:43 +02:00
|
|
|
|
1999-06-14 09:37:05 +02:00
|
|
|
<para>
|
2000-03-27 19:14:43 +02:00
|
|
|
Refer to the chapter in the
|
|
|
|
<citetitle>PostgreSQL Programmer's Guide</citetitle>
|
|
|
|
on the topic of extending
|
1999-07-22 17:09:15 +02:00
|
|
|
<productname>Postgres</productname> via functions
|
|
|
|
for further information on writing external functions.
|
1999-06-14 09:37:05 +02:00
|
|
|
</para>
|
1999-07-22 17:09:15 +02:00
|
|
|
|
1999-06-14 09:37:05 +02:00
|
|
|
<para>
|
1998-09-16 16:43:12 +02:00
|
|
|
Use <command>DROP FUNCTION</command>
|
2000-03-27 19:14:43 +02:00
|
|
|
to remove user-defined functions.
|
1999-06-14 09:37:05 +02:00
|
|
|
</para>
|
1999-05-20 04:57:15 +02:00
|
|
|
|
1999-07-22 17:09:15 +02:00
|
|
|
<para>
|
|
|
|
<productname>Postgres</productname> allows function "overloading";
|
|
|
|
that is, the same name can be used for several different functions
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
so long as they have distinct argument types. This facility must
|
|
|
|
be used with caution for <literal>internal</literal> and
|
|
|
|
C-language functions, however.
|
2000-03-27 19:14:43 +02:00
|
|
|
</para>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
The full <acronym>SQL92</acronym> type syntax is allowed for
|
|
|
|
input arguments and return value. However, some details of the
|
|
|
|
type specification (e.g. the precision field for
|
|
|
|
<type>numeric</type> types) are the responsibility of the
|
|
|
|
underlying function implementation and are silently swallowed
|
|
|
|
(e.g. not recognized or
|
|
|
|
enforced) by the <command>CREATE FUNCTION</command> command.
|
|
|
|
</para>
|
1999-05-20 04:57:15 +02:00
|
|
|
|
1999-07-22 17:09:15 +02:00
|
|
|
<para>
|
|
|
|
Two <literal>internal</literal>
|
|
|
|
functions cannot have the same C name without causing
|
|
|
|
errors at link time. To get around that, give them different C names
|
|
|
|
(for example, use the argument types as part of the C names), then
|
|
|
|
specify those names in the AS clause of <command>CREATE FUNCTION</command>.
|
|
|
|
If the AS clause is left empty then <command>CREATE FUNCTION</command>
|
|
|
|
assumes the C name of the function is the same as the SQL name.
|
|
|
|
</para>
|
1999-05-20 04:57:15 +02:00
|
|
|
|
1999-07-22 17:09:15 +02:00
|
|
|
<para>
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
When overloading SQL functions with C-language functions, give
|
|
|
|
each C-language instance of the function a distinct name, and use
|
|
|
|
the alternative form of the <command>AS</command> clause in the
|
|
|
|
<command>CREATE FUNCTION</command> syntax to ensure that
|
|
|
|
overloaded SQL functions names are resolved to the correct
|
|
|
|
dynamically linked objects.
|
1999-07-22 17:09:15 +02:00
|
|
|
</para>
|
|
|
|
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
|
1999-07-22 17:09:15 +02:00
|
|
|
<para>
|
|
|
|
A C function cannot return a set of values.
|
|
|
|
</para>
|
1999-06-14 09:37:05 +02:00
|
|
|
</refsect2>
|
1998-12-29 03:24:47 +01:00
|
|
|
</refsect1>
|
1998-05-13 07:34:00 +02:00
|
|
|
|
1999-06-14 09:37:05 +02:00
|
|
|
<refsect1 id="R1-SQL-CREATEFUNCTION-2">
|
|
|
|
<title>
|
1998-05-13 07:34:00 +02:00
|
|
|
Usage
|
1999-06-14 09:37:05 +02:00
|
|
|
</title>
|
|
|
|
<para>
|
1998-05-13 07:34:00 +02:00
|
|
|
To create a simple SQL function:
|
1999-07-06 19:16:42 +02:00
|
|
|
|
2000-03-27 19:14:43 +02:00
|
|
|
<programlisting>
|
1999-07-06 19:16:42 +02:00
|
|
|
CREATE FUNCTION one() RETURNS int4
|
|
|
|
AS 'SELECT 1 AS RESULT'
|
|
|
|
LANGUAGE 'sql';
|
|
|
|
SELECT one() AS answer;
|
|
|
|
|
2000-03-27 19:14:43 +02:00
|
|
|
<computeroutput>
|
2000-03-26 20:32:30 +02:00
|
|
|
answer
|
|
|
|
--------
|
|
|
|
1
|
2000-03-27 19:14:43 +02:00
|
|
|
</computeroutput>
|
|
|
|
</programlisting>
|
1999-07-06 19:16:42 +02:00
|
|
|
</para>
|
|
|
|
|
1998-05-13 07:34:00 +02:00
|
|
|
<para>
|
1999-07-22 17:09:15 +02:00
|
|
|
This example creates a C function by calling a routine from a user-created
|
1998-05-13 07:34:00 +02:00
|
|
|
shared library. This particular routine calculates a check
|
|
|
|
digit and returns TRUE if the check digit in the function parameters
|
|
|
|
is correct. It is intended for use in a CHECK contraint.
|
|
|
|
</para>
|
|
|
|
<programlisting>
|
1999-07-06 19:16:42 +02:00
|
|
|
CREATE FUNCTION ean_checkdigit(bpchar, bpchar) RETURNS bool
|
|
|
|
AS '/usr1/proj/bray/sql/funcs.so' LANGUAGE 'c';
|
1998-12-29 03:24:47 +01:00
|
|
|
|
1999-07-06 19:16:42 +02:00
|
|
|
CREATE TABLE product (
|
1999-06-14 09:37:05 +02:00
|
|
|
id char(8) PRIMARY KEY,
|
|
|
|
eanprefix char(8) CHECK (eanprefix ~ '[0-9]{2}-[0-9]{5}')
|
|
|
|
REFERENCES brandname(ean_prefix),
|
|
|
|
eancode char(6) CHECK (eancode ~ '[0-9]{6}'),
|
|
|
|
CONSTRAINT ean CHECK (ean_checkdigit(eanprefix, eancode))
|
1999-07-06 19:16:42 +02:00
|
|
|
);
|
1998-05-13 07:34:00 +02:00
|
|
|
</programlisting>
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
This example creates a function that does type conversion between the
|
|
|
|
user defined type complex, and the internal type point. The
|
|
|
|
function is implemented by a dynamically loaded object that was
|
|
|
|
compiled from C source. For <productname>Postgres</productname> to
|
|
|
|
find a type conversion function automatically, the sql function has
|
|
|
|
to have the same name as the return type, and overloading is
|
|
|
|
unavoidable. The function name is overloaded by using the second
|
2000-07-22 04:39:10 +02:00
|
|
|
form of the <command>AS</command> clause in the SQL definition:
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
</para>
|
|
|
|
<programlisting>
|
|
|
|
CREATE FUNCTION point(complex) RETURNS point
|
|
|
|
AS '/home/bernie/pgsql/lib/complex.so', 'complex_to_point'
|
|
|
|
LANGUAGE 'c';
|
|
|
|
</programlisting>
|
|
|
|
<para>
|
2000-07-22 06:30:27 +02:00
|
|
|
The C declaration of the function is:
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
</para>
|
|
|
|
<programlisting>
|
|
|
|
Point * complex_to_point (Complex *z)
|
|
|
|
{
|
|
|
|
Point *p;
|
|
|
|
|
|
|
|
p = (Point *) palloc(sizeof(Point));
|
|
|
|
p->x = z->x;
|
|
|
|
p->y = z->y;
|
|
|
|
|
|
|
|
return p;
|
|
|
|
}
|
|
|
|
</programlisting>
|
|
|
|
|
|
|
|
|
1999-06-14 09:37:05 +02:00
|
|
|
</refsect1>
|
1998-05-13 07:34:00 +02:00
|
|
|
|
1999-06-14 09:37:05 +02:00
|
|
|
<refsect1 id="R1-SQL-CREATEFUNCTION-4">
|
|
|
|
<title>
|
1998-05-13 07:34:00 +02:00
|
|
|
Compatibility
|
1999-06-14 09:37:05 +02:00
|
|
|
</title>
|
1999-07-06 19:16:42 +02:00
|
|
|
|
1999-06-14 09:37:05 +02:00
|
|
|
<refsect2 id="R2-SQL-CREATEFUNCTION-4">
|
1999-07-22 17:09:15 +02:00
|
|
|
<refsect2info>
|
2000-03-27 19:14:43 +02:00
|
|
|
<date>2000-03-25</date>
|
1999-07-22 17:09:15 +02:00
|
|
|
</refsect2info>
|
|
|
|
<title>
|
|
|
|
SQL92
|
|
|
|
</title>
|
|
|
|
|
|
|
|
<para>
|
|
|
|
<command>CREATE FUNCTION</command> is
|
|
|
|
a <productname>Postgres</productname> language extension.
|
|
|
|
</para>
|
|
|
|
</refsect2>
|
|
|
|
|
|
|
|
<refsect2 id="R2-SQL-CREATEFUNCTION-5">
|
1999-06-14 09:37:05 +02:00
|
|
|
<refsect2info>
|
2000-03-27 19:14:43 +02:00
|
|
|
<date>2000-03-25</date>
|
1999-06-14 09:37:05 +02:00
|
|
|
</refsect2info>
|
|
|
|
<title>
|
1998-09-16 16:43:12 +02:00
|
|
|
SQL/PSM
|
1999-06-14 09:37:05 +02:00
|
|
|
</title>
|
1998-09-16 16:43:12 +02:00
|
|
|
<para>
|
|
|
|
|
1999-07-06 19:16:42 +02:00
|
|
|
<note>
|
1998-05-13 07:34:00 +02:00
|
|
|
<para>
|
1998-09-16 16:43:12 +02:00
|
|
|
PSM stands for Persistent Stored Modules. It is a procedural
|
1998-05-13 07:34:00 +02:00
|
|
|
language and it was originally hoped that PSM would be ratified
|
1998-09-16 16:43:12 +02:00
|
|
|
as an official standard by late 1996. As of mid-1998, this
|
1999-07-06 19:16:42 +02:00
|
|
|
has not yet happened, but it is hoped that PSM will
|
1998-05-13 07:34:00 +02:00
|
|
|
eventually become a standard.
|
|
|
|
</para>
|
1999-07-06 19:16:42 +02:00
|
|
|
</note>
|
1998-09-16 16:43:12 +02:00
|
|
|
|
1999-07-06 19:16:42 +02:00
|
|
|
SQL/PSM <command>CREATE FUNCTION</command> has the following syntax:
|
|
|
|
<synopsis>
|
1998-09-16 16:43:12 +02:00
|
|
|
CREATE FUNCTION <replaceable class="parameter">name</replaceable>
|
I have been working with user defined types and user defined c
functions. One problem that I have encountered with the function
manager is that it does not allow the user to define type conversion
functions that convert between user types. For instance if mytype1,
mytype2, and mytype3 are three Postgresql user types, and if I wish to
define Postgresql conversion functions like
I run into problems, because the Postgresql dynamic loader would look
for a single link symbol, mytype3, for both pieces of object code. If
I just change the name of one of the Postgresql functions (to make the
symbols distinct), the automatic type conversion that Postgresql uses,
for example, when matching operators to arguments no longer finds the
type conversion function.
The solution that I propose, and have implemented in the attatched
patch extends the CREATE FUNCTION syntax as follows. In the first case
above I use the link symbol mytype2_to_mytype3 for the link object
that implements the first conversion function, and define the
Postgresql operator with the following syntax
The patch includes changes to the parser to include the altered
syntax, changes to the ProcedureStmt node in nodes/parsenodes.h,
changes to commands/define.c to handle the extra information in the AS
clause, and changes to utils/fmgr/dfmgr.c that alter the way that the
dynamic loader figures out what link symbol to use. I store the
string for the link symbol in the prosrc text attribute of the pg_proc
table which is currently unused in rows that reference dynamically
loaded
functions.
Bernie Frankpitt
1999-09-28 06:34:56 +02:00
|
|
|
( [ [ IN | OUT | INOUT ] <replaceable class="parameter">type</replaceable> [, ...] ] )
|
1998-09-16 16:43:12 +02:00
|
|
|
RETURNS <replaceable class="parameter">rtype</replaceable>
|
|
|
|
LANGUAGE '<replaceable class="parameter">langname</replaceable>'
|
|
|
|
ESPECIFIC <replaceable class="parameter">routine</replaceable>
|
|
|
|
<replaceable class="parameter">SQL-statement</replaceable>
|
1999-07-06 19:16:42 +02:00
|
|
|
</synopsis>
|
1998-05-13 07:34:00 +02:00
|
|
|
</para>
|
|
|
|
</refsect2>
|
|
|
|
</refsect1>
|
1999-06-14 09:37:05 +02:00
|
|
|
</refentry>
|
1998-05-13 07:34:00 +02:00
|
|
|
|
|
|
|
<!-- Keep this comment at the end of the file
|
|
|
|
Local variables:
|
2000-03-27 19:14:43 +02:00
|
|
|
mode:sgml
|
1999-06-14 09:37:05 +02:00
|
|
|
sgml-omittag:nil
|
1998-05-13 07:34:00 +02:00
|
|
|
sgml-shorttag:t
|
|
|
|
sgml-minimize-attributes:nil
|
|
|
|
sgml-always-quote-attributes:t
|
|
|
|
sgml-indent-step:1
|
|
|
|
sgml-indent-data:t
|
|
|
|
sgml-parent-document:nil
|
|
|
|
sgml-default-dtd-file:"../reference.ced"
|
|
|
|
sgml-exposed-tags:nil
|
2000-03-27 19:14:43 +02:00
|
|
|
sgml-local-catalogs:("/usr/lib/sgml/catalog")
|
1998-05-13 07:34:00 +02:00
|
|
|
sgml-local-ecat-files:nil
|
|
|
|
End:
|
|
|
|
-->
|