Thanks!
make_transient_to_detached did the trick!
ill add the answer to my question.
On Friday, 2 March 2018 11:56:30 UTC-5, Mike Bayer wrote:
>
> please add an answer to your stackoverflow question as well
>
> On Fri, Mar 2, 2018 at 11:55 AM, Mike Bayer <mik...@zzzcomputing.com
> <javascript:>> wrote:
> > On Fri, Mar 2, 2018 at 11:55 AM, Harshvardhan Gupta
> > <harsh...@gmail.com <javascript:>> wrote:
> >> I meant, do the query only when email is required, and not unless
> anything
> >> else is required.
> >> if I call merge(), the query is instantly emitted. I want it to be
> emitted
> >> only if an unloaded attribute is requested.
> >
> > make the object act like detached and expired, then associate with the
> session:
> >
> > from sqlalchemy.orm.session import make_transient_to_detached
> > a1 = A(id=1)
> > make_transient_to_detached(a1)
> > s.add(a1)
> >
> > print("-------------------")
> > assert a1.data == "some data"
> > assert len(a1.bs) == 3
> >
> >
> >
> >
> >
> >>
> >> On Friday, 2 March 2018 11:51:20 UTC-5, Mike Bayer wrote:
> >>>
> >>> On Fri, Mar 2, 2018 at 11:30 AM, Harshvardhan Gupta
> >>> <harsh...@gmail.com> wrote:
> >>> > There is no way to achieve what I want without doing the query?
> >>> > merge seems to do the whole query.
> >>>
> >>> you have a User row, and you want to load columns in that row, like
> >>> "full_name". How would you like to achieve that without emitting a
> >>> query?
> >>>
> >>>
> >>>
> >>> > I also have asked this question on stack overflow which talks about
> my
> >>> > use
> >>> > case :
> >>> >
> >>> >
> >>> >
> https://stackoverflow.com/questions/49062520/querying-properties-of-transient-models-in-sqlalchemy
>
> >>> >
> >>> >
> >>> > On Friday, 2 March 2018 11:27:31 UTC-5, Mike Bayer wrote:
> >>> >>
> >>> >> On Fri, Mar 2, 2018 at 11:21 AM, Harshvardhan Gupta
> >>> >> <harsh...@gmail.com> wrote:
> >>> >> > I also tried loading a related attribute , and it still returns
> None.
> >>> >>
> >>> >>
> >>> >> you need to merge the object:
> >>> >>
> >>> >> my_user = session.merge(my_user)
> >>> >>
> >>> >> that is your only option. E.g. do the query.
> >>> >>
> >>> >> >
> >>> >> >
> >>> >> > On Friday, 2 March 2018 11:00:47 UTC-5, Harshvardhan Gupta wrote:
> >>> >> >>
> >>> >> >> Thanks, I am able to call my object, but the attribute prints
> none:
> >>> >> >>
> >>> >> >>
> >>> >> >> E.g. my model is:
> >>> >> >>
> >>> >> >> class User(Dictifiable, db.Model, UserMixin):
> >>> >> >> __tablename__ = 'user'
> >>> >> >>
> >>> >> >> id = Column(Integer, Sequence('user_id_seq'),
> primary_key=True)
> >>> >> >> full_name = Column(String(50))
> >>> >> >>
> >>> >> >>
> >>> >> >> And this is what I have done :
> >>> >> >>
> >>> >> >> `u_lazy = User(id=1)`
> >>> >> >> `db.session().enable_relationship_loading(u_lazy)`
> >>> >> >> when i try to print u_lazy.full_name, it shows null (it is non
> null
> >>> >> >> in
> >>> >> >> db
> >>> >> >> )
> >>> >> >>
> >>> >> >>
> >>> >> >> On Friday, 2 March 2018 10:55:11 UTC-5, Mike Bayer wrote:
> >>> >> >>>
> >>> >> >>> On Fri, Mar 2, 2018 at 10:52 AM, Harshvardhan Gupta
> >>> >> >>> <harsh...@gmail.com> wrote:
> >>> >> >>> > Thanks for the reply.
> >>> >> >>> >
> >>> >> >>> > There is a guarantee that the user will exist ,why is why I
> want
> >>> >> >>> > to
> >>> >> >>> > prevent that extra db query.
> >>> >> >>> >
> >>> >> >>> > When I try to do enable relationship loading ,I get the error
> :
> >>> >> >>> > Scoped session has no attribute enable relationship loading.
> >>> >> >>>
> >>> >> >>> that's a scoped_session(), not a Session, access the Session by
> >>> >> >>> calling it: scoped_session().enable_relationship_loading(obj)
> >>> >> >>>
> >>> >> >>> >
> >>> >> >>> > --
> >>> >> >>> > SQLAlchemy -
> >>> >> >>> > The Python SQL Toolkit and Object Relational Mapper
> >>> >> >>> >
> >>> >> >>> > http://www.sqlalchemy.org/
> >>> >> >>> >
> >>> >> >>> > To post example code, please provide an MCVE: Minimal,
> Complete,
> >>> >> >>> > and
> >>> >> >>> > Verifiable Example. See http://stackoverflow.com/help/mcve
> for
> >>> >> >>> > a
> >>> >> >>> > full
> >>> >> >>> > description.
> >>> >> >>> > ---
> >>> >> >>> > You received this message because you are subscribed to the
> >>> >> >>> > Google
> >>> >> >>> > Groups "sqlalchemy" group.
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> >>> >> >>> > send
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> >>> >> >>> > For more options, visit https://groups.google.com/d/optout.
> >>> >> >
> >>> >> > --
> >>> >> > SQLAlchemy -
> >>> >> > The Python SQL Toolkit and Object Relational Mapper
> >>> >> >
> >>> >> > http://www.sqlalchemy.org/
> >>> >> >
> >>> >> > To post example code, please provide an MCVE: Minimal, Complete,
> and
> >>> >> > Verifiable Example. See http://stackoverflow.com/help/mcve for a
> full
> >>> >> > description.
> >>> >> > ---
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> >>> >> > For more options, visit https://groups.google.com/d/optout.
> >>> >
> >>> > --
> >>> > SQLAlchemy -
> >>> > The Python SQL Toolkit and Object Relational Mapper
> >>> >
> >>> > http://www.sqlalchemy.org/
> >>> >
> >>> > To post example code, please provide an MCVE: Minimal, Complete, and
> >>> > Verifiable Example. See http://stackoverflow.com/help/mcve for a
> full
> >>> > description.
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> >>
> >> --
> >> SQLAlchemy -
> >> The Python SQL Toolkit and Object Relational Mapper
> >>
> >> http://www.sqlalchemy.org/
> >>
> >> To post example code, please provide an MCVE: Minimal, Complete, and
> >> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> >> description.
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>
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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