Alter table remove column migration removes primary key

[pasibonfire]

Expected Behavior

Removing a column should remove only the column.
If the removed column is primary key, only then the constraint should be deleted.

Current Behavior

Migration that removes a column (or rollback for add column) removes the primary key constraint from the table.

Possible Solution

Adding primary_key: false doesn't remove the constraint. If this is expected behaviour, there is no documentation about it.

Steps to Reproduce (for bugs)

1. Clone https://github.com/pasibonfire/mssql_ecto.git
2. Checkout branch fix_remove_column
3. Run docker-compose build
4. Run docker-compose run mssql_ecto mix test

Context

Your Environment

• MssqlEcto version: 1.1.0
• Ecto version: 2.2.8
• Elixir version: 1.5.3
• Erlang version: 20
• Microsoft SQL Server version: microsoft/mssql-server-linux:2017-CU6
• Operating System and version: macOS High Sierra 10.13.4
• Link to your project: https://github.com/pasibonfire/mssql_ecto/tree/fix_remove_column