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.
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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