This is not how we do it. Constraints, columns, etc are removed using a post-deployment migration. This means you can't end up with NULL values and the likes.
This helps ensure database consistency, but might not actually avoid errors. In this scenario, the period of time between the app code being deployed and the post-deploy migration running there could potentially be application level errors because the app is now ignoring the deleted field and the database expects unique values (or non-null, or whatever constraints you have).
You can solve these issues with some creative migration paths both at the app level and at the database level, but those changes aren't always trivial, and may not necessarily fit in the pre-deploy post-deploy migration strategy.
This may also not be an issue for you. You may be willing to accept a brief period of time where an error is unlikely, but technically possible. Personally, most of the time this is acceptable to me, but I always find it important to think about these scenarios in case something does happen.
Comments
This is not how we do it. Constraints, columns, etc are removed using a post-deployment migration. This means you can't end up with NULL values and the likes.
This helps ensure database consistency, but might not actually avoid errors. In this scenario, the period of time between the app code being deployed and the post-deploy migration running there could potentially be application level errors because the app is now ignoring the deleted field and the database expects unique values (or non-null, or whatever constraints you have).
You can solve these issues with some creative migration paths both at the app level and at the database level, but those changes aren't always trivial, and may not necessarily fit in the pre-deploy post-deploy migration strategy.
This may also not be an issue for you. You may be willing to accept a brief period of time where an error is unlikely, but technically possible. Personally, most of the time this is acceptable to me, but I always find it important to think about these scenarios in case something does happen.