How to Best Handle Variable-Length Input Parameters in PostgreSQL Functions?

Employing Variable-Length Input Parameters in Functions

In the pursuit of customizing PostgreSQL stored procedures, a common approach involves creating a mode parameter to differentiate between different update scenarios in a single function. However, the optimal solution largely depends on the specific requirements and complexity of the task at hand.

Option 1: Utilizing Variadic Input Parameters

Variadic input parameters, like the mode parameter in the example, allow for a flexible number of arguments to be passed to the function. This flexibility is particularly useful for situations where the number of input parameters is not known in advance.

However, variadic parameters can be computationally expensive due to the additional overhead required to process the variable number of arguments.

Option 2: Single Default-Value Function

Using default values for function parameters is a simpler and more efficient solution for cases where some input parameters are optional but not null. By setting default values, you avoid the need for complex logic to handle missing parameters.

The example provided in the answer incorporates this approach efficiently:

CREATE OR REPLACE FUNCTION update_site(_name text, _city text DEFAULT NULL, _telephone int DEFAULT NULL)
  RETURNS int
  LANGUAGE plpgsql AS
$func$
BEGIN
   IF _city IS NULL AND _telephone IS NULL THEN
      RAISE WARNING 'At least one not-null input value required!';
      RETURN;  -- nothing to update
   END IF;

   UPDATE "Sites"
   SET    "City"      = COALESCE(_city, "City")
        , "Telephone" = COALESCE(_telephone, "Telephone")
   WHERE  "SiteName"  = _name;
END
$func$;

This function is more straightforward and computationally less intensive than the variadic approach.

Option 3: Multiple Specialized Functions

In cases where the purpose of each function is distinct, creating separate specialized functions for each task can be more efficient. By separating functionality into distinct functions, you can optimize each function for its specific purpose.

Conclusion

The best approach depends on the specific requirements of your application. For simple cases where only a few optional parameters exist, using default values for function parameters is a straightforward and efficient solution. For more complex scenarios involving a wide range of optional parameters, variadic input parameters or multiple specialized functions may be more appropriate.

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