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Tom Lane 2000-04-02 22:59:40 +00:00
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doc/src/sgml/xplang.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/xplang.sgml,v 1.7 2000/03/31 03:27:42 thomas Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/xplang.sgml,v 1.8 2000/04/02 22:59:40 tgl Exp $
-->
<chapter id="xplang">
@ -10,14 +10,19 @@ $Header: /cvsroot/pgsql/doc/src/sgml/xplang.sgml,v 1.7 2000/03/31 03:27:42 thoma
the definition of procedural languages.
In the case of a function or trigger
procedure defined in a procedural language, the database has
no builtin knowlege how to interpret the functions source
text. Instead, the calls are passed into
no built-in knowledge about how to interpret the function's source
text. Instead, the task is passed to
a handler that knows the details of the language. The
handler itself is a special programming language function
compiled into a shared object
and loaded on demand.
</para>
<para>
Writing a handler for a new procedural language (PL)
is outside the scope of this manual.
</para>
<sect1>
<title>Installing Procedural Languages</title>
@ -28,6 +33,9 @@ $Header: /cvsroot/pgsql/doc/src/sgml/xplang.sgml,v 1.7 2000/03/31 03:27:42 thoma
<para>
A procedural language is installed in the database in three steps.
(For the languages supplied with the standard distribution, the
shell script <filename>createlang</filename> can be used instead
of carrying out the details manually.)
</para>
<step performance="Required">
@ -39,10 +47,6 @@ $Header: /cvsroot/pgsql/doc/src/sgml/xplang.sgml,v 1.7 2000/03/31 03:27:42 thoma
configured in, the handler for PL/Tcl is also built
and installed in the same location.
</para>
<para>
Writing a handler for a new procedural language (PL)
is outside the scope of this manual.
</para>
</step>
<step performance="Required">
<para>
@ -53,8 +57,8 @@ CREATE FUNCTION <replaceable>handler_function_name</replaceable> ()
'<filename>path-to-shared-object</filename>' LANGUAGE 'C';
</programlisting>
The special return type of <acronym>OPAQUE</acronym> tells
the database, that this function does not return one of
the defined base- or composite types and is not directly usable
the database that this function does not return one of
the defined <acronym>SQL</acronym> datatypes and is not directly usable
in <acronym>SQL</acronym> statements.
</para>
</step>
@ -67,11 +71,12 @@ CREATE [ TRUSTED ] PROCEDURAL LANGUAGE '<replaceable>language-name</replaceable>
LANCOMPILER '<replaceable>description</replaceable>';
</programlisting>
The optional keyword <acronym>TRUSTED</acronym> tells
if ordinary database users that have no superuser
privileges can use this language to create functions
whether ordinary database users that have no superuser
privileges should be allowed to use this language to create functions
and trigger procedures. Since PL functions are
executed inside the database backend it should only be used for
languages that don't gain access to database backends
executed inside the database backend, the <acronym>TRUSTED</acronym>
flag should only be given for
languages that don't allow access to database backends
internals or the filesystem. The languages PL/pgSQL and
PL/Tcl are known to be trusted.
</para>
@ -83,7 +88,7 @@ CREATE [ TRUSTED ] PROCEDURAL LANGUAGE '<replaceable>language-name</replaceable>
<step performance="Required">
<para>
The following command tells the database where to find the
shared object for the PL/pgSQL languages call handler function.
shared object for the PL/pgSQL language's call handler function.
<programlisting>
CREATE FUNCTION plpgsql_call_handler () RETURNS OPAQUE AS
@ -116,7 +121,7 @@ CREATE TRUSTED PROCEDURAL LANGUAGE 'plpgsql'
functions call arguments and it's return data type. The source
text of the functions body is found in the prosrc attribute of
<literal>pg_proc</literal>.
Due to this, in contrast to C language functions, PL functions
Due to this, PL functions
can be overloaded like SQL language functions. There can be
multiple different PL functions having the same function name,
as long as the call arguments differ.