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 at
http://www.sqlalchemy.org/docs/mappers.html#using-relationships-with-inheritance
.
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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