On Wednesday, June 13, 2018 at 8:28:32 PM UTC-4, Mike Bayer wrote:
>
> On Wed, Jun 13, 2018 at 7:44 PM, Peter Lai <pete...@pw.utc.com
> <javascript:>> wrote:
> > I've implemented a Concrete inheritance model and Oracle 11g is balking
> on
> > `CAST(NULL AS CLOB) as fieldn` during the pjoin union query execution
> with:
> >
> > ORA-00932: inconsistent datatypes: expected - got CLOB
> >
> > This happens when the unioned tables representing the 2 subclasses have
> > different `Text` fields which are created as CLOBs on Oracle. This is
> > independent of cxOracle version, since we get the same problem running
> the
> > emitted query in native Oracle SQL Developer:
> >
> > `select cast(null as clob) from dual`
> >
> > ORA-00932: inconsistent datatypes: expected - got CLOB
> > 00932. 00000 - "inconsistent datatypes: expected %s got %s"
> > *Cause:
> > *Action:
> > Error at Line: 1 Column: 8
> >
> > The rest of the CASTs of NULL work fine, though, but generally NULL
> columns
> > should have no datatype in Oracle via NULL definition. I am on
> SQLAlchemy
> > 1.1.3. Does 1.2x handle this better? If yes, and I need to hotpatch,
> which
> > lines would I need to patch?
>
> just turn them off:
>
>
> http://docs.sqlalchemy.org/en/rel_1_1/orm/mapping_api.html?highlight=polymorphic_union#sqlalchemy.orm.util.polymorphic_union.params.cast_nulls
>
>
> cast_nulls¶ – if True, non-existent columns, which are represented as
> labeled NULLs, will be passed into CAST. This is a legacy behavior
> that is problematic on some backends such as Oracle - in which case it
> can be set to False.
>
>
Cool! However, I used/ am using AbstractConcreteBase for this and
apparently my inheritance-foo isn't good enough to avoid completely
copy-pasting a whole bunch of code from sqlalchemy.ext.declarative.api just
to override _create_polymorphic_union(). I tried to create a class that
inherits from AbstractConcreteBase for a simple override and I got a bunch
of `sqlalchemy.exc.ArgumentError: Mapper 'Mapper|FooBase|None' does not
have a mapped_table specified.` errors:
Base = declarative_base()
class AbstractConcreteBase_ORA(AbstractConcreteBase):
# override polymorphic union because of Oracle
@classmethod
def _create_polymorphic_union(cls, mappers):
return polymorphic_union(OrderedDict(
(mp.polymorphic_identity, mp.local_table)
for mp in mappers
), 'type', 'pjoin', False)
class FooBase(AbstractConcreteBase_ORA, Base):
common = Column(Integer, primary_key=True)
class Foo(FooBase, Base):
noncommon = Column(Text)
__mapper_args__ = {
'polymorphic_identity': 'foo',
'concrete': True
}
class Bar(FooBase, Base):
noncommon2 = Column(Text)
__mapper_args__ = {
'polymorphic_identity': 'bar',
'concrete': True
}
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