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On 02/09/2015 05:02 PM, Clint Byrum wrote:
> Excerpts from Jay Pipes's message of 2015-02-09 12:36:45 -0800:
>> CAS is preferred because it is measurably faster and more
>> obstruction-free than SELECT FOR UPDATE. A colleague of mine is almost
>> ready to publish documentation showing a benchmark of this that shows
>> nearly a 100% decrease in total amount of lock/wait time using CAS
>> versus waiting for the coarser-level certification timeout to retry the
>> transactions. As mentioned above, I believe this is due to the dramatic
>> decrease in ROLLBACKs.
>>
>
> I think the missing piece of the puzzle for me was that each ROLLBACK is
> an expensive operation. I figured it was like a non-local return (i.e.
> 'raise' in python or 'throw' in java) and thus not measurably different.
> But now that I think of it, there is likely quite a bit of optimization
> around the query path, and not so much around the rollback path.
>
> The bottom of this rabbit hole is simply exquisite, isn't it? :)

It is indeed. :) As soon as I think I understand it fully, a new problem 
area exposes itself.

Best,
-jay