That's a good precaution. Another one might be to log queries and check for use of that old column. 2 caveats: (1) ensure this logging doesn't cause performan

That's a good precaution. Another one might be to log queries and check for use of that old column. 2 caveats: (1) ensure this logging doesn't cause performance bottleneck and (2) this might not catch queries that use globs (ie. "select * from ..."). For (1) you can do this one only some of your instances of your DB cluster and (2), try to always use explicit column references.