Re: SELECT FOR UPDATE

Thomas Swan <tswan@idigx.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