Re: Waiting on a transaction

On Tue, 2005-08-16 at 12:01 -0700, Bill Moseley wrote:
> I wondered if my application should set an alarm and timeout
> with an error if, by odd chance, an update hangs.

Here's a way to handle this under the upcoming 8.1 release:

Before you execute the update you can execute SELECT ... FOR UPDATE
NOWAIT to select anything (e.g. dummy constant) from the row that you
want to update.  If no error is thrown then you have a lock on your row
and you can confidently proceed with your update.  Otherwise someone has
that row locked.  At that point you can loop and retry if you want.