On Jul 29, 2010, at 5:00 PM, Kent Bower wrote:
> Right. I understand. Thanks for pointing that out, you are correct.
>
> My bigger concern was getting the ArTranBase mapper correct. Apparently
> there is no need in this case to specify "with_polymorphic=" in the mapper.
> Did I miss documentation on using 'polymorphic_union' without
> "with_polymorphic="? That seems to be working, I was just looking for
> confirmation that this is a "supported" use-case.
that is probably correct.
>
>
>
> On 7/29/2010 4:51 PM, Michael Bayer wrote:
>> What I meant was, if you want to say session.query(ArTranBase), which it
>> appears that you do, then you are querying against ArTranBase.
>>
>> Since it seems like you want the polymorphic_union here, when you query
>> ArTranBase and you want it to eagerly load "trancode" and "paymenttype", it
>> would need to have a relation() on the ArTranBase mapper so that it knows
>> what to join.
>>
>>
>>
>>
>> On Jul 29, 2010, at 4:46 PM, Kent wrote:
>>
>>
>>> This seems to work, but I didn't find examples of this. Does this
>>> look correct (assuming there is no parent table in the database and
>>> all I really want is 2 'normal' mappers and a 3rd that performs a
>>> polymorphoric_union)?
>>>
>>> ==========================================
>>>
>>> artran_union = polymorphic_union({
>>> 'artran': artrans_table,
>>> 'archive': artransarchive_table
>>> }, 'type', 'artran_union')
>>>
>>> artranbase_mapper = mapper(ArTranBase, artran_union,
>>> polymorphic_on=artran_union.c.type)
>>>
>>>
>>> # ---------------------------- ArTran
>>> --------------------------------------- #
>>> mapper(ArTran, artrans_table, inherits=artranbase_mapper,
>>> concrete=True, polymorphic_identity='artran',
>>> properties={'trancode': relation(TranCode,
>>> cascade='refresh-expire,expunge', lazy=False),
>>> 'paymenttype': relation(PaymentType,
>>> cascade='refresh-expire,expunge', lazy=False)}
>>> )
>>>
>>>
>>> # ---------------------------- ArTranArchive
>>> --------------------------------------- #
>>> mapper(ArTranArchive, artransarchive_table,
>>> inherits=artranbase_mapper,
>>> concrete=True, polymorphic_identity='archive',
>>> properties={'trancode': relation(TranCode,
>>> cascade='refresh-expire,expunge', lazy=False),
>>> 'paymenttype': relation(PaymentType,
>>> cascade='refresh-expire,expunge', lazy=False)}
>>> )
>>>
>>>
>>>
>>> On Jul 29, 4:20 pm, Kent Bower<k...@retailarchitects.com> wrote:
>>>
>>>> No, in fact, there is no ArTranBase table at all.
>>>>
>>>> If I remove concrete inheritance, how do I issue a UNION of the two
>>>> tables and have the objects polymorphically loaded?
>>>>
>>>> On 7/29/2010 4:18 PM, Michael Bayer wrote:
>>>>
>>>>
>>>>> On Jul 29, 2010, at 2:31 PM, Kent wrote:
>>>>>
>>>>
>>>>>> I'm getting a messy error that could be a bug, but is very likely
>>>>>> related to my setup of a set of 2 polymorphic classes I am attempting
>>>>>> to map.
>>>>>>
>>>>
>>>>>> One entity is a "transaction" and the other is a "transaction_archive"
>>>>>> record. The table structure is therefore very similar for both tables
>>>>>> and it seems to fit Concrete Table Inheritance, except there is no
>>>>>> 'parent' entity. Rather, they are sister tables.
>>>>>>
>>>>
>>>>>> What I have mostly works until I get into loading this union as a
>>>>>> relation to another table... then I'm having problems.
>>>>>>
>>>>
>>>>>> I couldn't clearly see the "correct" way to set up this when there is
>>>>>> no real inheritance, but rather sister entities.
>>>>>>
>>>>
>>>>>> Can you suggest how to correctly map these 2 tables?
>>>>>>
>>>>
>>>>> it looks fine to me except you're asking for eager loading, and if you're
>>>>> querying from the ArTranBase you'd need to specify relationship() at that
>>>>> level (as well as on each child). Example
>>>>> athttp://www.sqlalchemy.org/docs/mappers.html#using-relationships-with-....
>>>>>
>>>>
>>>>> OTOH if you are not querying from ArTranBase, remove the usage of
>>>>> concrete inheritance altogether.
>>>>>
>>>>
>>>>>> ================================================
>>>>>> artran_union = polymorphic_union({
>>>>>> 'artran': artrans_table,
>>>>>> 'archive': artransarchive_table
>>>>>> }, 'type', 'artran_union')
>>>>>>
>>>>
>>>>>> artranbase_mapper = mapper(ArTranBase, artran_union,
>>>>>> with_polymorphic=('*', artran_union),
>>>>>> polymorphic_on=artran_union.c.type,
>>>>>> polymorphic_identity='ignored')
>>>>>>
>>>>
>>>>>> # ---------------------------- ArTran
>>>>>> --------------------------------------- #
>>>>>> mapper(ArTran, artrans_table, inherits=artranbase_mapper,
>>>>>> concrete=True, polymorphic_identity='artran',
>>>>>> properties={'trancode': relation(TranCode,
>>>>>> cascade='refresh-expire,expunge', lazy=False),
>>>>>> 'paymenttype': relation(PaymentType,
>>>>>> cascade='refresh-expire,expunge', lazy=False)}
>>>>>> )
>>>>>>
>>>>
>>>>>> # ---------------------------- ArTranArchive
>>>>>> --------------------------------------- #
>>>>>> mapper(ArTranArchive, artransarchive_table,
>>>>>> inherits=artranbase_mapper,
>>>>>> concrete=True, polymorphic_identity='archive',
>>>>>> properties={'trancode': relation(TranCode,
>>>>>> cascade='refresh-expire,expunge', lazy=False),
>>>>>> 'paymenttype': relation(PaymentType,
>>>>>> cascade='refresh-expire,expunge', lazy=False)}
>>>>>> )
>>>>>>
>>>>
>>>>>> Thanks in advance.
>>>>>>
>>>>
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>>>>>>
>>>>
>>>>
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