ALTER FUNCTION

Changes the definition of a function.

Synopsis

ALTER FUNCTION <name> ( [ [<argmode>] [<argname>] <argtype> [, ...] ] ) 
   <action> [, ... ] [RESTRICT]

ALTER FUNCTION <name> ( [ [<argmode>] [<argname>] <argtype> [, ...] ] )
   RENAME TO <new_name>

ALTER FUNCTION <name> ( [ [<argmode>] [<argname>] <argtype> [, ...] ] ) 
   OWNER TO <new_owner>

ALTER FUNCTION <name> ( [ [<argmode>] [<argname>] <argtype> [, ...] ] ) 
   SET SCHEMA <new_schema>

where action is one of:

{CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT}
{IMMUTABLE | STABLE | VOLATILE | [ NOT ] LEAKPROOF}
{[EXTERNAL] SECURITY INVOKER | [EXTERNAL] SECURITY DEFINER}
EXECUTE ON { ANY | MASTER | ALL SEGMENTS | INITPLAN }
COST <execution_cost>
SET <configuration_parameter> { TO | = } { <value> | DEFAULT }
SET <configuration_parameter> FROM CURRENT
RESET <configuration_parameter>
RESET ALL

Description

ALTER FUNCTION changes the definition of a function.

You must own the function to use ALTER FUNCTION. To change a function’s schema, you must also have CREATE privilege on the new schema. To alter the owner, you must also be a direct or indirect member of the new owning role, and that role must have CREATE privilege on the function’s schema. (These restrictions enforce that altering the owner does not do anything you could not do by dropping and recreating the function. However, a superuser can alter ownership of any function anyway.)

Parameters

name : The name (optionally schema-qualified) of an existing function.

argmode : The mode of an argument: either IN, OUT, INOUT, or VARIADIC. If omitted, the default is IN. Note that ALTER FUNCTION does not actually pay any attention to OUT arguments, since only the input arguments are needed to determine the function’s identity. So it is sufficient to list the IN, INOUT, and VARIADIC arguments.

argname : The name of an argument. Note that ALTER FUNCTION does not actually pay any attention to argument names, since only the argument data types are needed to determine the function’s identity.

argtype : The data type(s) of the function’s arguments (optionally schema-qualified), if any.

new_name : The new name of the function.

new_owner : The new owner of the function. Note that if the function is marked SECURITY DEFINER, it will subsequently run as the new owner.

new_schema : The new schema for the function.

CALLED ON NULL INPUT RETURNS NULL ON NULL INPUT STRICT : CALLED ON NULL INPUT changes the function so that it will be invoked when some or all of its arguments are null. RETURNS NULL ON NULL INPUT or STRICT changes the function so that it is not invoked if any of its arguments are null; instead, a null result is assumed automatically. See CREATE FUNCTION for more information.

IMMUTABLE STABLE VOLATILE : Change the volatility of the function to the specified setting. See CREATE FUNCTION for details.

[ EXTERNAL ] SECURITY INVOKER [ EXTERNAL ] SECURITY DEFINER : Change whether the function is a security definer or not. The key word EXTERNAL is ignored for SQL conformance. See CREATE FUNCTION for more information about this capability.

LEAKPROOF : Change whether the function is considered leakproof or not. See CREATE FUNCTION for more information about this capability.

EXECUTE ON ANY EXECUTE ON MASTER EXECUTE ON ALL SEGMENTS EXECUTE ON INITPLAN : The EXECUTE ON attributes specify where (coordinator or segment instance) a function runs when it is invoked during the query execution process.

: EXECUTE ON ANY (the default) indicates that the function can be run on the coordinator, or any segment instance, and it returns the same result regardless of where it is run. LightDB-A Database determines where the function runs.

: EXECUTE ON MASTER indicates that the function must run only on the coordinator instance.

: EXECUTE ON ALL SEGMENTS indicates that the function must run on all primary segment instances, but not the coordinator, for each invocation. The overall result of the function is the UNION ALL of the results from all segment instances.

: EXECUTE ON INITPLAN indicates that the function contains an SQL command that dispatches queries to the segment instances and requires special processing on the coordinator instance by LightDB-A Database when possible.

: For more information about the EXECUTE ON attributes, see CREATE FUNCTION.

COST execution_cost : Change the estimated execution cost of the function. See CREATE FUNCTION for more information.

configuration_parameter value : Set or change the value of a configuration parameter when the function is called. If value is DEFAULT or, equivalently, RESET is used, the function-local setting is removed, and the function runs with the value present in its environment. Use RESET ALL to clear all function-local settings. SET FROM CURRENT saves the value of the parameter that is current when ALTER FUNCTION is run as the value to be applied when the function is entered.

RESTRICT : Ignored for conformance with the SQL standard.

Notes

LightDB-A Database has limitations on the use of functions defined as STABLE or VOLATILE. See CREATE FUNCTION for more information.

Examples

To rename the function sqrt for type integer to square_root:

ALTER FUNCTION sqrt(integer) RENAME TO square_root;

To change the owner of the function sqrt for type integer to joe:

ALTER FUNCTION sqrt(integer) OWNER TO joe;

To change the schema of the function sqrt for type integer to math:

ALTER FUNCTION sqrt(integer) SET SCHEMA math;

To adjust the search path that is automatically set for a function:

ALTER FUNCTION check_password(text) RESET search_path;

Compatibility

This statement is partially compatible with the ALTER FUNCTION statement in the SQL standard. The standard allows more properties of a function to be modified, but does not provide the ability to rename a function, make a function a security definer, or change the owner, schema, or volatility of a function. The standard also requires the RESTRICT key word, which is optional in LightDB-A Database.