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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