Trying ZODB, background in Relational: mimic auto_increment?

[Diez B. Roggisch]

Jean-Paul Calderone schrieb:
> On Thu, 14 Aug 2008 16:15:11 +0200, "Diez B. Roggisch" 
> <deets at nospam.web.de> wrote:
>> Jean-Paul Calderone wrote:
>>
>>> On Thu, 14 Aug 2008 05:22:35 -0700 (PDT), Phillip B Oldham
>>> <phillip.oldham at gmail.com> wrote:
>>>> [snip]
>>>>
>>>> How would one assign a unique ID to the root at that point?
>>>
>>> Here's one way
>>>
>>>     class Sequence(Persistence):
>>>         def __init__(self):
>>>             self.current = 0
>>>
>>>         def next(self):
>>>             self.current += 1
>>>             return self.current
>>>
>>>     ticketSequence = Sequence()
>>>
>>>     class Ticket(Persistence):
>>>         def __init__(self):
>>>             self.id = ticketSequence.next()
>>
>> Be aware that this isn't working concurrently. Depending on your
>> application, this can be mitigated using a simple threading.Lock.
>>
> 
> ZODB has transactions.  That's probably the best way to make this
> code safe for concurrent use.

But that's a great deal more complicated! It requires merging, and while 
this of course is possible, you should have mentioned it because 
otherwise the OP might run into problems.

Diez