On Sun, Mar 22, 2009 at 8:17 AM, Michael Bayer <mike...@zzzcomputing.com>wrote:
>
> theres three layers to this issue. the first is, yes as_scalar() is
> trying to compile the expression which I don't think there's a very
> good reason, so ill likely commit a change for that (it will result in
> a behavioral change regarding the namespace of "someselect.c" but im
> hoping not one anyone was relying upon that).
Sounds good
> the second layer is,
> if you're casting against a constant value like below, or a column on
> the Order class, you don't need the select() - just say
> cast(...).label('foo') -
I'm not casting a constant (see below). I just simplified the expression
until I found the specific function causing the error.
however, convenient operations like "print
> query" still wont work since they evaulate the cast() without a
> dialect.
I like using print for debugging but I can live without it.
> the third is, the whole "cast can't compile without a
> dialect" thing is going away in 0.6, but I can't make it work in 0.5
> without major changes.
>
> One particular workaround that would totally eliminate the issue until
> 0.6 comes out would be to use the dialect-specific type for now, i.e.
> MSNumeric (mysql), PGNumeric (postgres), SLNumeric (sqlite).
>
>
I'm using SQLIte for unit tests and MySQL for production so I can't see a
way to do this.
I found that I CAN cast the result of the select (references OrderLine
table, not shown):
def IF(condition, true, false):
return case([(condition, true)], else_ = false)
class Order(Base):
-- Skipping Column Definitions --
L = OrderLine
taxable = column_property(
cast(select([func.sum(IF(L.taxable, L.quantity * L.price, 0))],
L.order_id == id).as_scalar(),
Numeric(14.2)).label("taxable"))
This isn't really the same thing because the float would be rounded after
the sum not line by line. I think I could also use sum(... type_ =
Numeric(14,2)) for the same result. Am I missing an easier way to do this?
>
>
> On Mar 22, 2009, at 6:27 AM, Shawn Church wrote:
>
> > >>> import sqlalchemy
> > >>> sqlalchemy.__version__
> > '0.5.2'
> >
> > >>> from sqlalchemy import *
> > >>> from sqlalchemy.orm import relation, column_property,
> > sessionmaker
> >
> > >>> from sqlalchemy.ext.declarative import declarative_base
> > >>> Base = declarative_base()
> > >>> Session = sessionmaker()
> >
> > >>> class Order(Base):
> > ... __tablename__ = "orders"
> > ...
> > ... id = Column(Integer, primary_key = True)
> > ...
> > ... test = column_property(select([cast(1,
> > Numeric(14,2))]).label("test"))
>
>
> >
>
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