I think at’s the best way to describe this issue, but it’s actually impossible.
Say we have ath brand new table called workflow_instance, and an existing table issue which has a column config. In a migration I want to copy the value of config into into new rows in workflow_instance. I then want to delete the config value from issue and add a workflow_instance_id instead. The problem is the don’t know which issue id’s the values of config come from.