ALTER FUNCTION
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## ALTER FUNCTION

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
    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 }
        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 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. If no argument list is specified, the name must be unique in its schema.

`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.

`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.

`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. See Section 37.11 for details. 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 need to do that.

`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 19 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 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) 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 PostgreSQL.

## See Also

CREATE FUNCTION, DROP FUNCTION, ALTER PROCEDURE, ALTER ROUTINE

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