How to avoid database deadlocks?

Question

Some database features, such as SELECT ... FOR UPDATE and ON DELETE CASCADE, are implicitly vulnerable to deadlocks because the database does not s

Answer 1

A few years wiser, I am revising the accepted answer to state that database deadlocks cannot be prevented.

If you are lucky enough to be able to break down database operations to only interact with a single table at a time (something that isn't always possible) then you are forced to choose between poor performance and the possibility of deadlocks. Pick your poison.

Answer 2

Just don't use those features which can cause deadlocks. ON DELETE CASCADE can be re-written in a way that forces an order and thus avoids deadlocks.

SELECT ... FOR UPDATE is specifically designed to allow you to avoid locks -- it lets you select and lock a row so you can keep a consistent order on all threads.

You do have to be careful how you use it, it could cause a deadlock if you don't understand the locking order of all your updates.