How Can I Automatically Drop All Overloads of a PostgreSQL Function?

Dropping Functions Without Parameter Knowledge

When maintaining a collection of functions in a text file with "CREATE OR REPLACE FUNCTION" syntax, it can become tedious to manually track and delete overloads when parameters are added or removed. This dilemma arises due to the need to specify each parameter type in the exact order when dropping a function.

To streamline this process, consider utilizing the following query to generate DROP FUNCTION commands automatically:

SELECT 'DROP FUNCTION ' || oid::regprocedure
FROM pg_proc
WHERE proname = 'my_function_name'
AND pg_function_is_visible(oid);

Explanation:

• The query scans the pg_proc system catalog to identify functions matching the specified name.
• The cast to regprocedure and then to text ensures proper formatting, including quotes and schema qualification where necessary.
• The pg_function_is_visible(oid) condition ensures that only functions visible in the current search path are considered.

Example Output:

DROP FUNCTION my_function_name(string text, form text, maxlen integer);
DROP FUNCTION my_function_name(string text, form text);
DROP FUNCTION my_function_name(string text);

The resulting DROP FUNCTION commands can be executed sequentially to remove all functions with the specified name, regardless of parameter count or type.

Additional Options:

• If desired, the SELECT query can be modified to restrict the selection to specific schemas or function signatures.
• An alternative approach is to create a PL/pgSQL function that encapsulates the DROP FUNCTION logic, allowing for immediate execution with a single function call. However, this should be used with caution due to its potential to inadvertently delete functions.

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