How to use long id in Rails applications?

How can I change the (default) type for ActiveRecord's IDs? int is not long enough, I would prefer long. I was surprised that there is no :long for the migrations - does one just use some decimal?

Credits to http://moeffju.net/blog/using-bigint-columns-in-rails-migrations

class CreateDemo < ActiveRecord::Migration
  def self.up
    create_table :demo, :id => false do |t|
      t.integer :id, :limit => 8
    end
  end
end

See the option :id => false which disables the automatic creation of the id field
The t.integer :id, :limit => 8 line will produce a 64 bit integer field

To set the default primary key column type, the migration files are not the place to mess with.

Instead, just stick this at the bottom of your config/environment.rb

ActiveRecord::ConnectionAdapters::MysqlAdapter::NATIVE_DATABASE_TYPES[:primary_key] = "BIGINT UNSIGNED DEFAULT NULL auto_increment PRIMARY KEY"

And all your tables should be created with the intended column type for id:

+--------------+---------------------+------+-----+---------+----------------+
| Field        | Type                | Null | Key | Default | Extra          |
+--------------+---------------------+------+-----+---------+----------------+
| id           | bigint(20) unsigned | NO   | PRI | NULL    | auto_increment |

After you've done what you've set out to do... the next question is probably "How do I make my foreign key columns the same column type?" since it does not make sense to have primary key people.id as bigint(20) unsigned, and person_id be int(11) or anything else?

For those columns, you can refer to the other suggestions, e.g.

t.column :author_id, 'BIGINT UNSIGNED'
t.integer :author_id, :limit => 8

UPDATE: @Notinlist, to use arbitrary column for primary key on arbitrary tables you need to do the create_table-change_column dance:

create_table(:users) do |t|
  # column definitions here..
end
change_column :users, :id, :float # or some other column type

e.g. if I wanted guid instead of auto-increment integers,

create_table(:users, :primary_key => 'guid') do |t|
  # column definitions here..
end
change_column :users, :guid, :string, :limit => 36

This is hard to set for the primary key with migrations because Rails puts it in automatically.

You can change any column later like this:

change_column :foobars, :something_id, 'bigint'

You can specify non-primary IDs as custom types in your initial migration like this:

create_table :tweets do |t|
  t.column :twitter_id, 'bigint'
  t.column :twitter_in_reply_to_status_id, 'bigint'
end

Where I have "bigint" you can put any text that your database would use for the database column type you want to use (e.g., "unsigned long").

If you need your id column to be a bigint, the easiest way to do it would be to create the table, then change the column in the same migration with change_column.

With PostgreSQL and SQLite, schema changes are atomic so this won't leave your database in a weird state if the migration fails. With MySQL you need to be more careful.

How to use long id in Rails applications?

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