id,summary,reporter,owner,description,type,status,component,version,severity,resolution,keywords,cc,stage,has_patch,needs_docs,needs_tests,needs_better_patch,easy,ui_ux 23386,Clear F expressions after a model instance is saved,codefisher,nobody,"I would have thought these two expresses would be exactly the same, except the second would be more efficient. A: some_model.some_field += 1 B: some_model.some_field = F('some_field') + 1 I hit some unexpected behaviour when, I did this some_model.save() # and somewhere far far away some_model.save() With A, the field is incremented once, as I expected. But with B, it gets incremented twice. I would have expected the F query to effect the next database call, and nothing more. It might be intended, but then it is not documented. I could write some come to demonstrate this. I only noticed it because I was using an import script that was creating lots of objects, and I had A and B in the model's overridden save method. They were causing vastly different results.",Cleanup/optimization,closed,"Database layer (models, ORM)",1.6,Normal,duplicate,,,Accepted,0,0,0,0,0,0