On Nov 17, 2008, at 7:50 AM, Iain wrote:
>
> I was wondering if anyone is aware of a way that I can customize the
> way query filters are written - possibly by some sort of customization
> of table columns?
>
> The issue is that I have some odd data/column types that can't be
> compared directly. That is, "SELECT * WHERE column1=value1" will not
> work - instead, I need to do "SELECT * WHERE user_func(column1)
> =user_func(value1)" or in some instances I want to do "SELECT * WHERE
> column2=user_func(value2)".
>
> So rather than everyone who writes queries having to remember to write
> these out as text or such, it'd be good if I could tell sqlalchemy to
> always re-write the queries that way whenever a user tests for
> equivalence on the relevant columns.
>
> Hope that makes sense!
you would implement this using a custom comparator class. Its a very
new feature that these are fully customizable, so this is how it looks
right now:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm.properties import ColumnProperty
Base = declarative_base()
class MyComparator(ColumnProperty.ColumnComparator):
def __eq__(self, other):
return func.lower(self.__clause_element__()) ==
func.lower(other)
class MyClass(Base):
__tablename__ = 'mytable'
id = Column(Integer, primary_key=True)
name = column_property(Column(String(50)),
comparator_factory=MyComparator)
sess = sessionmaker()()
print sess.query(MyClass).filter_by(name='SomeName').statement
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