```ruby
require 'bulk_insert/worker'

module BulkInsert
  extend ActiveSupport::Concern

  module ClassMethods
    def bulk_insert(*columns, values: nil, set_size:500)
      columns = default_bulk_columns if columns.empty?
      worker = BulkInsert::Worker.new(connection, table_name, columns, set_size)

      if values.present?
        transaction do
          worker.add_all(values)
          worker.save!
        end
        nil
      elsif block_given?
        transaction do
          yield worker
          worker.save!
        end
        nil
      else
        worker
      end
    end

    # helper method for preparing the columns before a call to :bulk_insert
    def default_bulk_columns
      self.column_names - %w(id)
    end

  end
end

ActiveRecord::Base.send :include, BulkInsert
```

Fix Rails 5 belongs_to behaviour override
user
```ruby
require 'bulk_insert/worker'

module BulkInsert
  extend ActiveSupport::Concern

  module ClassMethods
    def bulk_insert(*columns, values: nil, set_size:500)
      columns = default_bulk_columns if columns.empty?
      worker = BulkInsert::Worker.new(connection, table_name, columns, set_size)

      if values.present?
        transaction do
          worker.add_all(values)
          worker.save!
        end
        nil
      elsif block_given?
        transaction do
          yield worker
          worker.save!
        end
        nil
      else
        worker
      end
    end

    # helper method for preparing the columns before a call to :bulk_insert
    def default_bulk_columns
      self.column_names - %w(id)
    end

  end
end

ActiveSupport.on_load(:active_record) do
  send(:include, BulkInsert)
end
```
assistant