If you have recently migrated your rails application and tried the rails db:setup or rails db:schema:load commands, you might have noticed an error like this:

Column aaa_id on table bbb does not match column id on aaaa, which has type bigint(20). To resolve this issue, change the type of the aaa_id column on bbb to be :bigint. (For example t.bigint :aaa_id).

I will recommend the use of bigint if you are creating a new rails application, in the case of existing application, please add the following code into application.rb file to avoid this issue.

config.generators do |generator|
  generator.orm :active_record, primary_key_type: :integer
end

In the Schema.rb file, make sure that you mention id: :integer in create table block

Before

create_table "my_table", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|

After

create_table "my_table", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|