Re: SELECT FOR UPDATE

Thomas Swan <tswan(at)idigx(dot)com> writes:
>>> When a SELECT FOR UPDATE query is executed, are the row level locks on a
>>> table acquired in any specific order

Nope, just whatever order the chosen plan happens to visit the tuples
in.

> I had remembered several readings on ordered locking as a method to
> prevent deadlocks, and associated that with select for update
> methodology. In theory if you aquired locks in the following order, for
> each table/relation (in oid order) get rows/tuples (in oid order), you
> could help avoid deadlock by never gaining a lock ahead of someone
> else.

Hmmm .... this would only help for situations where all the locks of
interest are grabbed in a single scan. I suppose that has some
usefulness, but it can hardly be said to eliminate deadlocks. I kinda
doubt it's worth the trouble.

regards, tom lane