Thanks both Mike and Simon for the input! Apologies for the late reply, I've been trying to work this change into the non-example code, but ran into some issues. Disabling the Cascading Backrefs resolved the error in the sample, but I've stumbled onto a couple of different problems.
Something to note: I'm using the classical mapping approach and calling the mapper method direction. The issue in my own code base is that I'm seeing the following: tokyo.destinationGates = [Gate(id=null, name='westGate'), Gate(id=west gate's id, name='westGate')] The null id row is inserted after westGate's instantiation and the other is inserted after the merge+commit. I've attempted to reproduce the issue in a gist, but have run into something slightly different. In this new example, I'm getting an Instance <Location at 0x110dd0a50> has a NULL identity key. I think this should be 1:1 with the original example, but it looks like I may have missed something. I can post these questions separately, but I figured since it is related to the original issue I'd post here. The gist can be found below: https://gist.github.com/funseiki/3ddb35f849ed3c9bfb38eae404e7b8b4 On Monday, November 23, 2020 at 10:01:53 AM UTC-5 Simon King wrote: > I think your situation is described here: > > > https://docs.sqlalchemy.org/en/14/orm/session_state_management.html#merge-tips > > I'm not certain, but my guess is that when you create westGate, you > cause a *copy* of typeDict['gate'] to be merged into the current > session (because the merge cascades across the objectType > relationship). This instance is marked as pending. Then when you try > to create eastGate, the same thing happens again, but now there is > *already* a pending copy of typeDict['gate'] in the session, so you > get an error. > > The easiest solution would be to create a session-specific copy of > typeDict, either by re-querying from the database, or by using > session.merge with load=False. > > Hope that helps, > > Simon > > On Thu, Nov 19, 2020 at 11:16 PM Vinit Shah <elysium...@gmail.com> wrote: > > > > 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". > > > > 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 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. > > To unsubscribe from this group and stop receiving emails from it, send > an email to sqlalchemy+...@googlegroups.com. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/4d01df93-16ed-45a4-82f3-de04a8e57bcbn%40googlegroups.com > . > -- 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. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. 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