My code, in the “normal” case, would add a previously non-existent foreign key constraint with referential macro. The inverse (rollback) case would be for the constraint to be dropped, so I found that ecto documentation’s example where normal and reverse cases are both using referential to be insufficient to figure out what the from: clause should be for “no constraint”.
So it would still have to be some form of execute with SQL statements (e.g. create constraint if not exists... and drop constraint if exists) as opposed to being able to use the from: keyword’s argument to reverse the creation of foreign key constraint?
