On 12/11/2015 04:39 PM, Ofir Herzas wrote:
> Hi Mike,
> I've just checked my code and I noticed that I already use existing_type
> (not sure what was wrong with the documentation in that aspect).
>
> Can you elaborate a bit on specifying custom rules as you mentioned?
> I tried issuing a drop_constraint before calling the alter_column but
> that doesn't stop alter_column from trying to remove the check
> constraint by itself, leading to the same exception.
> On the other hand, I didn't see any parameter in the alter_column method
> that accepts a constraint name
You can call the drop_constraint(), then when you do the alter_column,
inside the existing_type put "create_constraint=False", so that it sees
it as an un-constrainted type.
drop_contraint('constraint_name')
alter_column('table', 'column', type=NewType(),
existing_type=Boolean(create_constraint=False))
>
> Thanks,
> Ofir
>
>
> On Thursday, December 10, 2015 at 3:39:42 PM UTC+2, Ofir Herzas wrote:
>
> I'm trying to run an alter_column operation from a Boolean type
> column to SmallInteger on Oracle.
>
> According to the documentation: "...Type changes which are against
> the SQLAlchemy “schema” types |Boolean|
>
> <http://www.sqlalchemy.org/docs/core/type_basics.html#sqlalchemy.types.Boolean>
> and |Enum|
>
> <http://www.sqlalchemy.org/docs/core/type_basics.html#sqlalchemy.types.Enum>
> may
> also add or drop constraints which accompany those types on backends
> that don’t support them natively.
> The |existing_server_default| argument is used in this case as well
> to remove a previous constraint...."
>
> Does this mean that the alter column should work out-of-the-box or
> do I have to remove the constraint myself because I'm getting the
> following error on alembic 0.8.3 (sqlalchemy 1.0.9):
>
> |
> sqlalchemy.exc.CompileError:Can't emit DROP CONSTRAINT for
> constraint CheckConstraint(<sqlalchemy.sql.elements.BinaryExpression
> object at 0x28a9b10>, name='_unnamed_', table=Table('t_message',
> MetaData(bind=None), Column('is_bulletin', Boolean(),
> table=<t_message>), schema=None),
> _create_rule=<sqlalchemy.util.langhelpers.portable_instancemethod
> object at 0x289ac68>, _type_bound=True); it has no name
> |
>
>
> And on a previous version (alembic 0.6.5, sqlalchemy 0.9.7) I got
> the following error:
>
> |
> sqlalchemy.exc.DatabaseError:(DatabaseError)ORA-02443:Cannotdrop
> constraint -nonexistent constraint
> 'ALTER TABLE t_message DROP CONSTRAINT None'{}
> |
>
>
> Your help will be appreciated...
>
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