Make Sqlalchemy Use Date In Filter Using Postgresql

Question

I\'m trying to perform the following query in Sqlalchemy.

Select * from \"Mytable\" where Date(date_time_field) = \"2011-08-16\";

I have tried

Answer 1

Native SQL functions can be invoked using using func module

from sqlalchemy import func
from datetime import date

my_data = session.query(MyObject).filter(
    func.date(MyObject.date_time) == date.today()
).all()

Calling func.date

 from sqlalchemy import select, func
 print select([func.date('2004-10-19 10:23:54')])

will produce following SQL:

 SELECT date(:date_2) AS date_1

You can also declare your own shortcuts to SQL functions:

from sqlalchemy.sql.functions import GenericFunction
from sqlalchemy.types import DateTime

class convert_tz(GenericFunction):
    """
    Sqlalchemy shortcut to SQL convert timezone function

    :param DateTime datetime
    :param str from_tz: The timezone the datetime will be converted from
    :param str to_tz: The timezone the datetime will be converted from
    :returns: Datetime in another timezone
    :rtype: DateTime or None if timezones are invalid

    """
    type = DateTime

Used like:

from sqlalchemy import select, func
print select([func.convert_tz(func.now(), '+00:00', '-05:00')])

It will generate following SQL:

SELECT convert_tz(now(), :param_1, :param_2) AS convert_tz_1