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> | CURRENT_USER | SESSION_USER }

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

ALTER FUNCTION <name> [ ( [ [<argmode>] [<argname>] <argtype> [, ...] ] ) ]
   DEPENDS ON EXTENSION <extension_name>

-- 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 }
    PARALLEL { UNSAFE | RESTRICTED | SAFE }
    EXECUTE ON { ANY | COORDINATOR | ALL SEGMENTS | INITPLAN }
    COST <execution_cost>
    ROWS <result_rows>
    SUPPORT <support_function>
    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. If no argument list is specified, the name must be unique in its schema.

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.

extension_name

The name of the extension that the function is to depend on.

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.

PARALLEL

Change whether the function is deemed safe for parallelism. See CREATE FUNCTION for details.

LEAKPROOF

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

EXECUTE ON ANY
EXECUTE ON COORDINATOR
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. Cloudberry Database determines where the function runs.

EXECUTE ON COORDINATOR 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 Cloudberry 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.

ROWS result_rows

Change the estimated number of rows returned by a set-returning function. See CREATE FUNCTION for more information.

SUPPORT support_function

Set or change the planner support function to use for this function. You must be superuser to use this option.

This option cannot be used to remove the support function altogether, since it must name a new support function. Use CREATE OR REPLACE FUNCTION if you require that.

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. See SET for more information about allowed parameter names and values.

RESTRICT

Ignored for conformance with the SQL standard.

Notes

Cloudberry 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 maths:

ALTER FUNCTION sqrt(integer) SET SCHEMA maths;

To mark the function sqrt for type integer as being dependent on the extension mathlib:

ALTER FUNCTION sqrt(integer) DEPENDS ON EXTENSION mathlib;

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

ALTER FUNCTION check_password(text) search_path = admin, pg_temp;

To disable automatic setting of search_path for a function:

ALTER FUNCTION check_password(text) RESET search_path;

The function will now execute with whatever search path is used by its caller.

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, attach configuration parameter values to a function, or change the owner, schema, or volatility of a function. The standard also requires the RESTRICT key word, which is optional in Cloudberry Database.

See also

CREATE FUNCTION, DROP FUNCTION, ALTER PROCEDURE, ALTER ROUTINE