Preventing Empty Updates In PostgreSQL Tables Using A Simple Trigger Function

The Need for Preventing Empty Updates

Empty updates are silent problems in PostgreSQL, occurring when an UPDATE makes no real changes to data. They're wasteful and can lead to loops in scenarios with recursive triggers.

Some common causes of empty updates include:

• Triggers meant to maintain data integrity can trigger loops if they update the same table. This leads to inefficiencies.
• Two tables need to stay in sync. Changes in one table trigger updates in the other, and vice versa. Mismanagement can lead to recursive circular updates, causing empty updates and performance issues.

The Solution: A Simple Trigger Function

CREATE OR REPLACE FUNCTION prevent_empty_update()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
DECLARE
BEGIN
    if old is not distinct from new then
        return null;
    end if;

    return new;
END;
$function$;

• The if old is not distinct from new then condition evaluates if the old and new data are the same. If they are identical, it means that the update does not change any values in the row, and the function returns null.
• If the condition is not met, indicating that the update will make changes to the row, the function returns new, allowing the update to proceed.

Application Of The Trigger Function

To put this trigger function into action, you need to apply it to the specific tables where you want to prevent empty updates.
Use the BEFORE UPDATE trigger to execute the prevent_empty_update() function for each row before the update is performed.

CREATE TRIGGER prevent_empty_updates
BEFORE UPDATE ON your_table
FOR EACH ROW
EXECUTE FUNCTION prevent_empty_update();

By implementing this trigger function, you can improve the efficiency and reliability of your PostgreSQL database, reducing the risk of unnecessary data modifications and recursive loops.