## Name

ALTER FUNCTION — change 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

    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
        COST execution_cost
        ROWS result_rows
        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 doesn't do anything you couldn't 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: `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 execute 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.

`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.

`configuration_parameter`
`value`

  Add or change the assignment to be made to a configuration parameter when the function is called. If `value` is `DEFAULT` or, equivalently, `RESET` is used, the function-local setting is removed, so that the function executes 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 executed as the value to be applied when the function is entered.

  See SET and Chapter 18, Server Configuration for more information about allowed parameter names and values.

`RESTRICT`

  Ignored for conformance with the SQL standard.

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

    ALTER FUNCTION check_password(text) SET 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 Postgres Pro.

## See Also

CREATE FUNCTION, DROP FUNCTION