Clarification, I can't make changes to the underlying *database* (i.e.
change the PK) but I can change my SA mapping. I did make the mapping
change and it seems to run like a champ now, updating the env_id before
either inserting or updating the row. Thanks everyone for your help!
Shawn
On Thursday, September 27, 2012 1:06:14 PM UTC-4, Shawn Wheatley wrote:
>
>
>
>> session.merge only looks at the primary key of the instance you are
>> inserting (it pays no attention to unique constraints). In your
>> example, the table contains a single row with PK (1, 1), and you are
>> merging an instance with PK (1, 4). SA sees these as different, so it
>> tries to INSERT the new row.
>>
>> If (1, 4) is actually the new version of (1, 1), then I would say that
>> your primary key should just be the acct_id column, not the pair of
>> (acct_id, env_id). SA will then see them as the same row, and UPDATE
>> rather than INSERT.
>>
>> Simon
>>
>
> While I agree with you philosophically, Simon, this utility is for an
> off-the-shelf application, so I can't make changes to the underlying data
> structure. I could, however, remove "env_id" as a primary key:
>
> class CiAcctK(DeclarativeBase):
> __tablename__ = 'ci_acct_k'
>
> __table_args__ = {}
>
> #column definitions
> acct_id = Column(u'acct_id', CHAR(length=10),
> ForeignKey('ci_acct.acct_id'), primary_key=True, unique=True,
> nullable=False)
> env_id = Column(u'env_id', NUMERIC(precision=6, scale=0),
> primary_key=False, nullable=False)
>
> Will this mapping cause any issues, given that the acct_id/env_id pair
> really *is* the primary key?
>
> Shawn
>
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