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 several methods. Some here on SO.
But none seems "realistic" since some do Casts Other String Formating ?!?! and not a plain simple Date() ( By Date i Mean the Postgresql Date not the Python One) at the ORM Field.

Is it possible at the ORM level to declare a Simple Date() around the queried field?

Asked By: PythonWolf

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Source

Answer 1

in postgreSQL if date_time_field is one field of your table then quer must like this.
Select * from Mytable where date_time_field = ‘2011-08-16’

Answered By: Turkesh Patel

Answer 2

To keep it clean for any web search.

from sqlalchemy import Date, cast
from datetime import date

my_data = session.query(MyObject).
filter(cast(MyObject.date_time,Date) == date.today()).all()

Answered By: PythonWolf

Answer 3

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

Answered By: Zuzia Hartleb

Answer 4

Here are generic solution that also works in SQLite:

day = date.today()
next_day = day + timedelta(days=1)
my_data = session.query(MyObject).filter(MyObject.date_time >= day,  MyObject.date_time < next_day).all()

Answered By: NMO

Make Sqlalchemy Use Date In Filter Using Postgresql

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