Clarence Gardner <clarence@silcom.com> writes:
> I noticed the following in some of our code today:
> select ... <join list> ... for update of a, b;
> Inasmuch as the cardinal rule for avoiding deadlocks is to acquire
> locks in a consistent order, should such a construction be avoided
> in favor of two separate "select ... for update" statements so that
> the order of acquisition of a and b is known?
If you're worried about deadlock, what you should be worrying about is
the order in which the individual rows are visited --- and splitting
this into two SQL commands doesn't in itself guarantee more about that
than the command as given.
regards, tom lane