Bump.
On Jan 10, 2012, at 12:06 , Martijn Moeling wrote:
> Hi,
>
> I am running into something
>
> I am using MySQL but am moving to Postgress so I'm looking for something
> compatible with the two.
>
> I have to generate an unique number for each record created into a column
> separate from the Id, call it SerialNumber
>
> I have found the Sequence object.
>
> Say I make the following class:
>
>
> class Order(Base):
> __tablename__ = 'product'
> Id = Column(Integer, primary_Key=True)
> SerialNr = Column(Integer,
> Sequence('SerialNumber'))
>
>
> after the create_all()
>
> CreateSequence('SerialNumber')
>
> All fine.
>
> Now I need to import data from the current production system. This data
> already has Serialnumbers generated.
>
> What should I do to make this work? Do I need the sequence created after the
> Import and set the Start value to the last imported SerialNumber+1 ?
> I would prefer creating the sequence before the import and "Update" the
> Sequence after the import.
>
> I can also "Drop" and Recreate after the import. The Import will be done
> several times during the test period. After the code is in production, I'll
> never ever need to modify the seqence anymore.
> Adding another table with just one column and setting SerialNr as a
> ForeignKey might be a solution too (As SerialNr will also be a coded as a 4
> character string which needs to be in the database for compatability reasons)
> I prefer the sequence though.
>
> My real code is much more complex, the above example class is simplified. In
> fact Order is a polymorphic base table and the sequence Column is in the
> polymorphic "child" tables only where Orders are in fact Items to be
> produced. The simplified version above is just to make things clear.
>
> Martijn
>
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