fix(#153): Ghost objects removed from the in-memory python list of the parent#160
fix(#153): Ghost objects removed from the in-memory python list of the parent#160Anubhav-2003 wants to merge 3 commits intocorridor:mainfrom
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…t of the parent When we were reverting a relationship where a child object was marked for deletion, it was not being removed from the Python's in-memory data-structure (collection). This left 'ghost' objects in the collection. If an autoflush occurred, SQLAlchemy attempted to lazy-load deferred columns for these ghost objects, causing a KeyError: Deferred loader failed crash, which was especially prevalent if we had a polymorphic sub-class. This fix ensures the items are actively removed from the collection list in memory using collection.remove(value), keeping the Python state perfectly synced with the database session state.
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| assert len(reverted_car.parts) == 0 | ||
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| with pytest.raises(IndexError): |
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assert len(reverted_car.parts) == 0 should be enough?
you can try doing self.session.flush() and check that it should not raise KeyError (to reproduce original error mentioned in commit msg).
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assert len(reverted_car.parts) == 0should be enough?you can try doing
self.session.flush()and check that it should not raiseKeyError(to reproduce original error mentioned in commit msg).
Thank You Ashish for nudging me in the right direction. So essentially the key error was still happening when I tried to flush, so just removing the deleted objects from the in-memory python list wasn't enough. So what I did now is essentially ensure that if something is not in memory and it is already marked for deletion then it is never lazy loaded, and the record just marks it with None. This actually matches the pattern of how we handle non-polymorphic objects, when we can't safely read a value from a deleted object.
Please let me know if I need to make any more changes,
Regards,
Anubhav
…properly triggering lazy-loads on deleted rows.
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When we were reverting a relationship where a child object was marked for deletion, it was not being removed from the Python's in-memory data-structure (collection). This left 'ghost' objects in the collection. If an autoFlush occurred, SQLAlchemy attempted to lazy-load deferred columns for these ghost objects, causing a KeyError: Deferred loader failed crash, which was especially prevalent if we had a polymorphic sub-class. This fix ensures the items are actively removed from the collection list in memory using collection.remove(value), keeping the Python state perfectly synced with the database session state.