grape

Gitlab::Database::MigrationHelpers#change_column_type_using_background_migration

Changes the column type of a table using a background migration.

Because this method uses a background migration it's more suitable for
large tables. For small tables it's better to use
`change_column_type_concurrently` since it can complete its work in a
much shorter amount of time and doesn't rely on Sidekiq.

Example usage:

    class Issue < ActiveRecord::Base
      self.table_name = 'issues'

      include EachBatch

      def self.to_migrate
        where('closed_at IS NOT NULL')
      end
    end

    change_column_type_using_background_migration(
      Issue.to_migrate,
      :closed_at,
      :datetime_with_timezone
    )

Reverting a migration like this is done exactly the same way, just with
a different type to migrate to (e.g. `:datetime` in the above example).

relation - An ActiveRecord relation to use for scheduling jobs and
           figuring out what table we're modifying. This relation _must_
           have the EachBatch module included.

column - The name of the column for which the type will be changed.

new_type - The new type of the column.

batch_size - The number of rows to schedule in a single background
             migration.

interval - The time interval between every background migration.

Source | Google | Stack overflow