|The PostgreSQL 9.0 Reference Manual - Volume 2 - Programming Guide
by The PostgreSQL Global Development Group
Paperback (6"x9"), 478 pages
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8.1 Installing Procedural Languages
A procedural language must be “installed” into each
database where it is to be used. But procedural languages installed in
template1 are automatically available in all
subsequently created databases, since their entries in
template1 will be copied by
So the database administrator can
decide which languages are available in which databases and can make
some languages available by default if desired.
For the languages supplied with the standard distribution, it is
only necessary to execute
language_name to install the language into the
current database. Alternatively, the program
createlang can be used to do this from the shell
command line. For example, to install the language
PL/Perl into the database
createlang plperl template1
The manual procedure described below is only recommended for
installing custom languages that
does not know about.
Manual Procedural Language Installation :
A procedural language is installed in a database in five steps,
which must be carried out by a database superuser. (For languages
- The shared object for the language handler must be compiled and installed into an appropriate library directory. This works in the same way as building and installing modules with regular user-defined C functions does; see section 5.9.6 Compiling and Linking Dynamically-Loaded Functions. Often, the language handler will depend on an external library that provides the actual programming language engine; if so, that must be installed as well.
The handler must be declared with the command
CREATE FUNCTION handler_function_name() RETURNS language_handler AS 'path-to-shared-object' LANGUAGE C;The special return type of
language_handlertells the database system that this function does not return one of the defined SQL data types and is not directly usable in SQL statements.
Optionally, the language handler can provide an “inline”
handler function that executes anonymous code blocks
DOcommands) written in this language. If an inline handler function is provided by the language, declare it with a command like
CREATE FUNCTION inline_function_name(internal) RETURNS void AS 'path-to-shared-object' LANGUAGE C;
Optionally, the language handler can provide a “validator”
function that checks a function definition for correctness without
actually executing it. The validator function is called by
CREATE FUNCTIONif it exists. If a validator function is provided by the language, declare it with a command like
CREATE FUNCTION validator_function_name(oid) RETURNS void AS 'path-to-shared-object' LANGUAGE C;
The PL must be declared with the command
CREATE [TRUSTED] [PROCEDURAL] LANGUAGE language-name HANDLER handler_function_name [INLINE inline_function_name] [VALIDATOR validator_function_name] ;The optional key word
TRUSTEDspecifies that the language does not grant access to data that the user would not otherwise have. Trusted languages are designed for ordinary database users (those without superuser privilege) and allows them to safely create of functions and trigger procedures. Since PL functions are executed inside the database server, the
TRUSTEDflag should only be given for languages that do not allow access to database server internals or the file system. The languages PL/pgSQL, PL/Tcl, and PL/Perl are considered trusted; the languages PL/TclU, PL/PerlU, and PL/PythonU are designed to provide unlimited functionality and should not be marked trusted.
CREATE LANGUAGE, the second through fourth steps can be omitted, because they will be carried out automatically if needed.)
section 8.1 Installing Procedural Languages shows how the manual installation procedure would work with the language PL/Perl.
Manual Installation of PL/Perl:
The following command tells the database server where to find the shared object for the PL/Perl language's call handler function:
CREATE FUNCTION plperl_call_handler() RETURNS language_handler AS '$libdir/plperl' LANGUAGE C;
PL/Perl has an inline handler function and a validator function, so we declare those too:
CREATE FUNCTION plperl_inline_handler(internal) RETURNS void AS '$libdir/plperl' LANGUAGE C; CREATE FUNCTION plperl_validator(oid) RETURNS void AS '$libdir/plperl' LANGUAGE C;
CREATE TRUSTED PROCEDURAL LANGUAGE plperl HANDLER plperl_call_handler INLINE plperl_inline_handler VALIDATOR plperl_validator;
then defines that the previously declared functions
should be invoked for functions and trigger procedures where the
language attribute is
In a default PostgreSQL installation, the handler for the PL/pgSQL language is built and installed into the “library” directory; furthermore, the PL/pgSQL language itself is installed in all databases. If Tcl support is configured in, the handlers for PL/Tcl and PL/TclU are built and installed in the library directory, but the language itself is not installed in any database by default. Likewise, the PL/Perl and PL/PerlU handlers are built and installed if Perl support is configured, and the PL/PythonU handler is installed if Python support is configured, but these languages are not installed by default.
|ISBN 9781906966065||The PostgreSQL 9.0 Reference Manual - Volume 2 - Programming Guide||See the print edition|