On Wed, Oct 10, 2018 at 4:40 PM Benjamin Bertrand <bee...@gmail.com> wrote:
>
> Hi,
>
> I'm trying to index some data from my postgres database to elasticsearch. I
> do something similar to what is described in this blog post:
> https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-xvi-full-text-search
> I store the new or modified objects in the before_flush event and want to
> store a representation of the object in the after_commit event.
>
> My issue is that I have some relationships in my objects and the following
> exception is raised by sqlalchemy:
> sqlalchemy.exc.InvalidRequestError: This session is in 'committed' state; no
> further SQL can be emitted within this transaction.
so you need to disable expire_on_commit, since you want the data there
inside of after_commit there is no way around this:
session = Session(engine, expire_on_commit=False)
it's likely you might want to use a different event hook for what
you're trying to do as the above is not ideal. after_flush_postexec()
might be a better choice as that is prior to the expiration.
then you need to load all the attributes somewhere ahead of time,
here's doing it inside of before_flush:
@event.listens_for(Session, "before_flush")
def before_flush(session, flush_context, instances):
# ...
if isinstance(obj, (Device, Host)):
# ...
for attr in inspect(obj).attrs:
getattr(obj, attr.key)
where again, you can query the database inside of
after_flush_postexec() without issue and no pre-load is needed. If
you are trying to only print at the after_commit boundary, then place
the state you want into your session._changes, like the actual strings
you're looking to print, then just print those.
>
> Here is a short example to illustrate the issue:
>
> import itertools
> from sqlalchemy import event, Column, Integer, String, ForeignKey,
> create_engine
> from sqlalchemy.orm import Session, relationship
> from sqlalchemy.ext.declarative import declarative_base
>
>
> Base = declarative_base()
>
>
> @event.listens_for(Session, "before_flush")
> def before_flush(session, flush_context, instances):
> session._changes = []
> for obj in itertools.chain(session.new, session.dirty):
> print(f"before_flush: {obj}")
> if isinstance(obj, (Device, Host)):
> session._changes.append(obj)
>
>
> @event.listens_for(Session, "after_commit")
> def after_commit(session):
> print("after_commit")
> for obj in session._changes:
> print(obj.to_dict())
>
>
> class User(Base):
> __tablename__ = "user_account"
> id = Column(Integer, primary_key=True)
> username = Column(String, nullable=False, unique=True)
>
> def __str__(self):
> return self.username
>
>
> class Device(Base):
> __tablename__ = "device"
> id = Column(Integer, primary_key=True)
> name = Column(String)
> user_id = Column(ForeignKey("user_account.id"), nullable=False, default=1)
> host_id = Column(Integer, ForeignKey("host.id"))
> user = relationship("User")
>
> def __str__(self):
> return self.name
>
> def to_dict(self):
> return {
> "id": self.id,
> "name": self.name,
> "user": str(self.user),
> "host": str(self.host),
> }
>
>
> class Host(Base):
> __tablename__ = "host"
> id = Column(Integer, primary_key=True)
> name = Column(String)
> devices = relationship("Device", backref="host")
>
> def __str__(self):
> return self.name
>
> def to_dict(self):
> return {
> "id": self.id,
> "name": self.name,
> "devices": [device.to_dict() for device in self.devices],
> }
>
>
> # engine = create_engine("postgresql://postgres:secret@localhost/test",
> echo=True)
> engine = create_engine("postgresql://postgres:secret@localhost/test")
> Base.metadata.drop_all(engine)
> Base.metadata.create_all(engine)
> session = Session(engine)
>
> user = User(id=1, username="John")
> session.add(user)
> session.commit()
>
> # If I don't query the user to add it to the session, I get:
> # sqlalchemy.exc.InvalidRequestError:
> # This session is in 'committed' state; no further SQL can be emitted within
> this transaction.
> myuser = session.query(User).get(1)
> device1 = Device(name="mydevice")
> session.add(device1)
> session.commit()
>
> host1 = Host(name="test")
> session.add(host1)
> # This raises sqlalchemy.exc.InvalidRequestError when trying to access
> host1.devices
> session.commit()
>
>
> How can I make sure that all relationships are in the session before the
> after_commit event?
>
> --
> 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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