Ruby-on-rails – How to change a nullable column to not nullable in a Rails migration

migrationruby-on-rails

I created a date column in a previous migration and set it to be nullable. Now I want to change it to be not nullable. How do I go about doing this assuming there are null rows in that database? I'm ok with setting those columns to Time.now if they're currently null.

Best Answer

If you do it in a migration then you could probably do it like this:

# Make sure no null value exist
MyModel.where(date_column: nil).update_all(date_column: Time.now)

# Change the column to not allow null
change_column :my_models, :date_column, :datetime, null: false

Related Solutions

Ruby-on-rails – How to write a migration to rename an ActiveRecord model and its table in Rails

Here's an example:

class RenameOldTableToNewTable < ActiveRecord::Migration
  def self.up
    rename_table :old_table_name, :new_table_name
  end

  def self.down
    rename_table :new_table_name, :old_table_name
  end
end

I had to go and rename the model declaration file manually.

Edit:

In Rails 3.1 & 4, ActiveRecord::Migration::CommandRecorder knows how to reverse rename_table migrations, so you can do this:

class RenameOldTableToNewTable < ActiveRecord::Migration
  def change
    rename_table :old_table_name, :new_table_name
  end 
end

(You still have to go through and manually rename your files.)

Ruby-on-rails – Rails migrations: Undo default setting for a column

Rails 5+

def change
  change_column_default( :table_name, :column_name, from: nil, to: false )
end

Rails 3 and Rails 4

def up
  change_column_default( :table_name, :column_name, nil )
end

def down
  change_column_default( :table_name, :column_name, false )
end