I found the following CTE demo (http://www.sqlalchemy.org/trac/
attachment/ticket/1859/cte_demo.py) and I was wondering if there was
any way to map these selects.
I have built a CTE based select to generate a dates table on the fly
and I would love to be able to map this and use generative selects to
transform queries. I have only been able to make the mapping work
with .from_statement() however this does not allow for
transformations.
Any thoughts?
Thanks,
-Marc
with CommonTableExpression.create('all_dates', ['date']) as all_dates:
start_exp = cast(bindparam('start'), DateTime)
end_exp = cast(bindparam('stop'), DateTime)
exp = func.DATEADD( literal_column('dd'), bindparam('step'),
all_dates.c.date )
s1 = select([start_exp])
s2 = select([exp], from_obj=all_dates).where(exp <= end_exp)
s = s1.union_all(s2)
all_dates = SelectFromCTE(all_dates, s)
class Date(object):
query = Session.query_property()
@classmethod
def range(cls, start, stop, step=1):
return
cls.query.from_statement(str(all_dates)).params(start=start,
stop=stop, step=step)
mapper(Date, all_dates, primary_key=[all_dates.c.date])
print Date.range('2011-01-01 00:00:00', '2021-01-01 00:00:00').all()
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