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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