On 06/24/2017 09:44 PM, phix1...@gmail.com wrote:
Am Freitag, 23. Juni 2017 05:25:41 UTC+2 schrieb Mike Bayer:
return my_col * literal(0.5, Float())
Hello Mike,
thank you for the quick response.
This doesn't seem to fully work when querying the value using
session.query(MyObject.my_hybrid_expression).scalar().
https://bitbucket.org/zzzeek/sqlalchemy/issues/4018/maintaining-float-type-affinity
is added as a proposal to use something more specific than type affinity
for this match however as always, these are all convenience behaviors
that are tunable when they fail to produce the desired effect; you can
control the exact type of any expression using type_coerce() or cast():
from sqlalchemy import Float, Integer, literal, Numeric, type_coerce
expr = literal(5, Integer) * literal(4.5, Float)
expr = type_coerce(expr, Numeric(asdecimal=False))
assert expr.type.asdecimal is False
From the
callstack, the Numeric (possibly representing the result of the
multiplication) now seems to be initialized by type_api.py:to_instance,
which calls the Numeric constructor without passing any **kwargs, so it
again defaults to asdecimal=True. This method is called by
sqltypes.py:_DateAffinity.Comparator._adapt_expression, which finds
MyFloat._type_affinity == Numeric.
Greetings,
Phillip
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