From cb8b40e6d5dbaa6a8ada4a6b1db2686a0f1e1f68 Mon Sep 17 00:00:00 2001 From: Peter Eisentraut Date: Sat, 19 May 2001 09:01:10 +0000 Subject: Allow special '$libdir' macro to show up in object file path in CREATE FUNCTION command. Guard against trying to load a directory. Update documentation some. --- doc/src/sgml/ref/create_function.sgml | 445 +++++++++++++++------------------- 1 file changed, 193 insertions(+), 252 deletions(-) (limited to 'doc/src/sgml/ref/create_function.sgml') diff --git a/doc/src/sgml/ref/create_function.sgml b/doc/src/sgml/ref/create_function.sgml index 6be24029b10..b95c2fd24e6 100644 --- a/doc/src/sgml/ref/create_function.sgml +++ b/doc/src/sgml/ref/create_function.sgml @@ -1,187 +1,151 @@ - - CREATE FUNCTION - + CREATE FUNCTION SQL - Language Statements + - - CREATE FUNCTION - - - Defines a new function - + CREATE FUNCTION + Defines a new function + - - 2000-03-25 - - -CREATE FUNCTION name ( [ ftype [, ...] ] ) - RETURNS rtype - AS definition + +CREATE FUNCTION name ( [ argtype [, ...] ] ) + RETURNS rettype + AS 'definition' LANGUAGE 'langname' [ WITH ( attribute [, ...] ) ] -CREATE FUNCTION name ( [ ftype [, ...] ] ) - RETURNS rtype - AS obj_file , link_symbol - LANGUAGE 'langname' +CREATE FUNCTION name ( [ argtype [, ...] ] ) + RETURNS rettype + AS 'obj_file', 'link_symbol' + LANGUAGE 'langname' [ WITH ( attribute [, ...] ) ] - + + - - - 2000-03-25 - - - Inputs - - + + Description - - - name - - - The name of a function to create. - - - - - ftype - - - The data type(s) of the function's arguments, if any. - The input types may be base or complex types, or - opaque. - Opaque indicates that the function - accepts arguments of a non-SQL type such as char *. - - - - - rtype - - - The return data type. - The output type may be specified as a base type, complex type, - , - or . - The - modifier indicates that the function will return a set of items, - rather than a single item. - - - - - attribute - - - An optional piece of information about the function, used for - optimization. See below for details. - - - - - definition - - - A string defining the function; the meaning depends on the language. - It may be an internal function name, the path to an object file, - an SQL query, or text in a procedural language. - - - - - obj_file , link_symbol - - - This form of the AS clause is used for - 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 - function. The string obj_file is the name of the file - containing the dynamically loadable object, and link_symbol is the object's link - symbol, that is the name of the function in the C - language source code. - - - - - langname - - - May be 'sql', - 'C', 'internal', - or 'plname', - where 'plname' - is the name of a created procedural language. See - - for details. - - - - - - - - - - 2000-03-25 - - - Outputs - - + + CREATE FUNCTION defines a new function. - - - -CREATE - - - - This is returned if the command completes successfully. - - - - - - - + + Parameters - - - 2000-03-25 - - - Description - - - CREATE FUNCTION allows a - Postgres user - to register a function - with the database. Subsequently, this user is considered the - owner of the function. + + name + + + + The name of a function to create. The name need not be unique, + because functions may be overloaded, but functions with the + same name must have different argument types. + + + + + + argtype + + + + The data type(s) of the function's arguments, if any. The + input types may be base or complex types, or + opaque. Opaque indicates + that the function accepts arguments of a non-SQL type such as + char *. + + + + + + rettype + + + + The return data type. The output type may be specified as a + base type, complex type, setof type, or + opaque. The setof + modifier indicates that the function will return a set of + items, rather than a single item. Functions with a declared + return type of opaque do not return a value. + These cannot be called directly; trigger functions make use of + this feature. + + + + + + definition + + + + A string defining the function; the meaning depends on the + language. It may be an internal function name, the path to an + object file, an SQL query, or text in a procedural language. + + + + + + obj_file, link_symbol + + + + This form of the AS clause is used for + 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 function. The string obj_file is the name of the + file containing the dynamically loadable object, and + link_symbol is the + object's link symbol, that is, the name of the function in the C + language source code. + + + + + + langname + + + + May be 'sql', 'C', + 'internal', or 'plname', where 'plname' is the name of a + created procedural language. See + + for details. + + + + + + attribute + + + + An optional piece of information about the function, used for + optimization. See below for details. + + + + + - - - 2000-08-24 - - - Function Attributes - + + The user that creates the function becomes the owner of the function. + - - The following items may appear in the WITH clause: + + The following attributes may appear in the WITH clause: @@ -214,17 +178,12 @@ CREATE - + - + - - - 2000-03-25 - - - Notes - + + Notes Refer to the chapter in the @@ -240,7 +199,7 @@ CREATE - The full SQL92 type syntax is allowed for + The full SQL type syntax is allowed for input arguments and return value. However, some details of the type specification (e.g., the precision field for numeric types) are the responsibility of the @@ -250,7 +209,7 @@ CREATE - Postgres allows function "overloading"; + Postgres allows function overloading; that is, the same name can be used for several different functions so long as they have distinct argument types. This facility must be used with caution for internal and C-language functions, however. @@ -275,38 +234,45 @@ CREATE C-language implementation of each overloaded SQL function. - + + When repeated CREATE FUNCTION calls refer to + the same object file, the file is only loaded once. To unload and + reload the file (perhaps during development), use the command. + + + - - - Usage - + + Examples + To create a simple SQL function: - -CREATE FUNCTION one() RETURNS int4 - AS 'SELECT 1 AS RESULT' + +CREATE FUNCTION one() RETURNS integer + AS 'SELECT 1 AS RESULT;' LANGUAGE 'sql'; -SELECT one() AS answer; - +SELECT one() AS answer; + answer -------- 1 - - + + - This example creates a C function by calling a routine from a user-created - 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. - - -CREATE FUNCTION ean_checkdigit(bpchar, bpchar) RETURNS boolean + The next example creates a C function by calling a routine from a + user-created 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 + constraint. + + +CREATE FUNCTION ean_checkdigit(char, char) RETURNS boolean AS '/usr1/proj/bray/sql/funcs.so' LANGUAGE 'c'; CREATE TABLE product ( @@ -316,28 +282,28 @@ CREATE TABLE product ( eancode char(6) CHECK (eancode ~ '[0-9]{6}'), CONSTRAINT ean CHECK (ean_checkdigit(eanprefix, eancode)) ); - - + + 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 Postgres to - find a type conversion function automatically, the sql function has + compiled from C source. For PostgreSQL to + find a type conversion function automatically, the SQL function has to have the same name as the return type, and so overloading is unavoidable. The function name is overloaded by using the second form of the AS clause in the SQL definition: - - + + CREATE FUNCTION point(complex) RETURNS point AS '/home/bernie/pgsql/lib/complex.so', 'complex_to_point' LANGUAGE 'c'; - - - The C declaration of the function is: - - + + + The C declaration of the function could be: + + Point * complex_to_point (Complex *z) { Point *p; @@ -348,58 +314,33 @@ Point * complex_to_point (Complex *z) return p; } - - - + + + - - - Compatibility - - - - - 2000-03-25 - - - SQL92 - + + Compatibility - - CREATE FUNCTION is - a Postgres language extension. - - - - - - 2000-03-25 - - - SQL/PSM - - + + A CREATE FUNCTION command is defined in SQL99. + The PostgreSQL version is similar but + not compatible. The attributes are not portable, neither are the + different available languages. + + - - - PSM stands for Persistent Stored Modules. It is a procedural - language. SQL/PSM is a standard to enable function extensibility. - - - - SQL/PSM CREATE FUNCTION has the following syntax: - -CREATE FUNCTION name - ( [ [ IN | OUT | INOUT ] type [, ...] ] ) - RETURNS rtype - LANGUAGE 'langname' - ESPECIFIC routine - SQL-statement - - - + + + See Also + + + , + , + PostgreSQL Programmer's Guide + +