I posted this on StackOverflow a few days ago, but I haven't been able to
figure this one out yet. The original post can be found here: StackOverflow:
object "is already present in this session"
<https://stackoverflow.com/questions/64897088/sqlalchemy-object-is-already-present-in-this-session-when-using-a-new-sessio>
.
I'm seeing the below error:
sqlalchemy.exc.InvalidRequestError: Can't attach instance <ObjectType at
0x10592fe50>; another instance with key ( <class '__main__.ObjectType'>,
(1,), None) is already present in this session.
I'm seeing this issue when I try to instantiate a new object that has a
foreign key relationship with an existing object that was created in
another session.
This happens in a few different cases in my actual code, but in the
provided sample it occurs with the following steps:
1. Add a new object into a new session
2. Close session and remove() from scoped_session
3. Reference the object in two newly constructed ones via their relationship
4. Error appears on the second object
# typeDict just contains a pre-fetched ObjectTypes
tokyo = Location(name="tokyo", objectType=typeDict['location'])
tokyo = write(tokyo)
# If I clear out the current session here, the error will occur
scopedSessionFactory().close()
scopedSessionFactory.remove()
westGate = Gate(name="westGate", destination=tokyo,
objectType=typeDict['gate'])
westGate = write(westGate)
luggage = LocationInput(name="luggage",
objectType=typeDict['locationinput'])
luggage = write(luggage)
# This is the line where the error occurs
eastGate = Gate(name="eastGate", origin=tokyo,
destinationInput=luggage, objectType=typeDict['gate'])
eastGate = write(eastGate)
I'm not sure what exactly causes this or way. For this example, I could
just reuse the same session, but I'd like to be able to take an object from
one closed session and add as a relationship field to another.
Full code sample available here:
https://gist.github.com/funseiki/a73424bebfb0d809e6d934f699a725bf
--
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
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