PostgreSQL Alter Function Examples

In PostgreSQL, the ALTER FUNCTION statement is used to modify the definition of an existing function. It allows you to change various attributes and behaviors of a function without having to drop and recreate it. This can be useful when you need to update the functionality of a function or fix any issues without affecting its dependencies.

Syntax

The basic syntax of the ALTER FUNCTION statement is as follows:

ALTER FUNCTION function_name ([argument_data_types]) [CASCADE | RESTRICT]
    attribute_to_modify;

Here’s an explanation of the components of the syntax:

ALTER FUNCTION: This is the main clause that indicates the intention to modify a function.
function_name: This is the name of the function that you want to alter.
[argument_data_types]: This optional part allows you to specify the data types of the function’s arguments. If the function has overloaded variants, you can specify the specific variant you want to alter by providing the argument data types.
[CASCADE | RESTRICT]: These are optional keywords that determine the behavior when the function is referenced by other database objects. If you specify CASCADE, the modifications will propagate to dependent objects. If you specify RESTRICT, the modification will fail if there are any dependent objects.
attribute_to_modify: This part specifies the specific attribute or behavior of the function that you want to alter. It can include options such as RENAME TO, OWNER TO, SET SCHEMA, SET DATA TYPE, SET DEFAULT, etc.

Let’s look at some examples of using ALTER FUNCTION:

Alter the name of a function:

ALTER FUNCTION my_function_name() 
RENAME TO new_function_name;

Change the owner of a function:

ALTER FUNCTION my_function_name() 
OWNER TO new_owner;

Modify the data type of a function’s argument:

ALTER FUNCTION my_function_name(integer) 
SET DATA TYPE bigint;

Change the default value of a function’s argument:

ALTER FUNCTION my_function_name(integer DEFAULT 10) 
SET DEFAULT 20;

Examples

ALTER FUNCTION set_customers
(p_first_name varchar, p_last_name varchar) 
RENAME TO add_customers;

ALTER FUNCTION set_customers
(p_first_name varchar, p_last_name varchar) 
OWNER TO user_1;

ALTER FUNCTION set_customers
(p_first_name varchar, p_last_name varchar) 
SET SCHEMA test_schema;

It’s important to note that the specific attributes you can modify using ALTER FUNCTION depend on the available options for functions in PostgreSQL. The documentation provides detailed information on the available options and syntax for altering functions.

Remember to exercise caution when altering functions, as it can have implications for dependent objects and the overall functionality of your database.