I have to work with a old database which stores almost all information as
strings (VARCHAR, NCHAR). To create a usable interface, I tought of
creating a UserDefinedType or a TypeDecorator to convert the values which
are fed to the database or loaded from the database.
Both versions seem to work when used like this:
class IntegerString(types.UserDefinedType):
def get_col_spec(self):
return 'NCHAR'
def column_expression(self, col):
return sa.func.CONVERT(sa.literal_column('INT'), col)
class TestType(types.TypeDecorator):
impl = types.NCHAR
def process_bind_param(self, value, dialect):
return str(value)
def process_result_value(self, value, dialect):
return int(value)
Where the IntergerString works at the database level and the TestType works
at the application level. However, what is missing is type conversion if
the column is used in Where Clauses. Is there a method to apply the type
conversion at the database level for where clauses?
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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