PostgreSQL - Drop Procedure

In PostgreSQL 11 and later, support for stored procedures was introduced. Unlike functions, stored procedures can be used to perform transactions within their body, among other capabilities. If you need to remove a stored procedure, you can use the DROP PROCEDURE command.

Basic Syntax:

DROP PROCEDURE [IF EXISTS] procedure_name([argument_types]) [CASCADE | RESTRICT];

IF EXISTS: An optional keyword to prevent an error if the procedure doesn't exist. If the procedure doesn't exist and you don't use this clause, an error will be raised.
procedure_name: The name of the procedure you want to drop.
argument_types: A comma-separated list of the data types of the procedure's arguments. This is necessary because PostgreSQL allows procedure overloading, meaning you can have multiple procedures with the same name but different argument lists.
CASCADE: This option will automatically drop objects that depend on the procedure.
RESTRICT: This is the default behavior. It prevents the procedure from being dropped if any objects depend on it.

Example:

Drop a Simple Procedure:
Let's say you have a procedure named update_records that takes a single integer argument:
```
DROP PROCEDURE update_records(integer);
```
Using IF EXISTS:
If you're unsure whether a procedure exists and want to avoid an error in case it doesn't:
```
DROP PROCEDURE IF EXISTS update_records(integer);
```

Important Considerations:

Procedure Overloading: As PostgreSQL allows procedure overloading, you must specify the argument types to uniquely identify which version of the procedure you intend to drop.
Dependencies: If other database objects depend on the procedure, you might need to use the CASCADE option to automatically drop those objects as well. Be cautious when using CASCADE to ensure you understand the implications and potential cascading deletions.
Permissions: Only the owner of the procedure or a superuser can drop a procedure.
Backup: It's a best practice to always backup your database before making significant changes, like dropping procedures.

By exercising caution and always double-checking the procedure name and its arguments, you can ensure that you're dropping the intended procedure without unintentionally affecting other parts of your database.

Removing stored procedures in PostgreSQL:
- Description: Use DROP FUNCTION to remove a stored procedure.
- Code:
```
DROP FUNCTION your_procedure_name(argument_type1, argument_type2);
```
Dropping procedures with specific signatures in PostgreSQL:
- Description: Specify the function signatures to drop procedures with particular parameter types.
- Code:
```
DROP FUNCTION IF EXISTS your_procedure_name(argument_type1, argument_type2) CASCADE;
```

Handling dependencies when dropping procedures in PostgreSQL:

Description: Drop dependent objects (e.g., triggers) before removing a procedure.

Code:

-- Drop dependent objects first
DROP TRIGGER your_trigger_name ON your_table;

-- Drop the procedure
DROP FUNCTION your_procedure_name(argument_type1, argument_type2);

Using DROP PROCEDURE IF EXISTS in PostgreSQL:
- Description: Safely drop a procedure if it exists.
- Code:
```
DROP FUNCTION IF EXISTS your_procedure_name(argument_type1, argument_type2) CASCADE;
```
Cascading options with DROP PROCEDURE in PostgreSQL:
- Description: Use CASCADE to automatically drop dependent objects.
- Code:
```
DROP FUNCTION your_procedure_name(argument_type1, argument_type2) CASCADE;
```
Dropping procedures with multiple schemas in PostgreSQL:
- Description: Specify the schema when dropping a procedure in a non-default schema.
- Code:
```
DROP FUNCTION schema_name.your_procedure_name(argument_type1, argument_type2);
```

Dropping built-in procedures in PostgreSQL:

Description: Custom functions can't be dropped, but you can replace them with your own implementation.

Code:

CREATE OR REPLACE FUNCTION pg_catalog.your_builtin_function(argument_type1, argument_type2)
RETURNS return_type
LANGUAGE sql
AS $$
-- Your implementation
$$;

Recovering space after dropping procedures in PostgreSQL:
- Description: Reclaim disk space after dropping procedures using the VACUUM command.
- Code:
```
-- Full vacuum on the entire PostgreSQL instance
VACUUM FULL;
-- Analyze for statistics update
ANALYZE;
```