Re: Concurrency

Simon Riggs <simon@2ndquadrant.com> writes:
> On Mon, 2005-05-09 at 12:21 -0500, Kris Kiger wrote:
>> Quick question.  I lock a table, call it table X, and then issue two
>> updates on that table.  The two updates are left waiting.  I then unlock
>> the table.   The two updates go through.  My question is, is there a
>> predictable way to determine which query will be executed first?

> The lock queue is served in FIFO sequence.

... usually.  We will promote later arrivals in front of older ones if
the alternative would be a deadlock (eg, the later one already holds
some lock that would block the earlier one).

            regards, tom lane