Re: FW: Fw: [Springframework-developer] insert functionality in j dbc package

[Isabelle M. <isa...@me...>]

Hi Dmitryi,

I'm incorporating your code into Spring, and am just now looking at RdbmsMaxValueIncrementer.
I feel pretty uneasy about this code, as I think it could lead to duplicate values of the key being handed out. This because the actions of selecting and writing out the new value are separate. Consider this :

(1) the current max value is 5
(2) connection 1 does select (max+1) and receives 6
(3) connection 1 goes off and does some work with the value 6 in mind
(4) connection 2 does select (max+1) and receives 6
(5) connection 1 commits, this is ok
(6) connection 2 commits and gets a duplicate key exception

I understand your rationale for the code -- after all, what does one do with some unknown database -- but I think we should comment the code as being potentially unsafe.

Isabelle

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