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Defines the primary key field. Use of the native PostgreSQL UUID type is supported, and can be used by defining your tables as such:
create_table :stuffs, id: :uuid do |t|
t.string :content
t.timestamps
end
By default, this will use the +gen_random_uuid()+ function from the pgcrypto extension. As that extension is only available in PostgreSQL 9.4+, for earlier versions an explicit default can be set to use +uuid_generate_v4()+ from the uuid-ossp extension instead:
create_table :stuffs, id: false do |t|
t.primary_key :id, :uuid, default: "uuid_generate_v4()"
t.uuid :foo_id
t.timestamps
end
To enable the appropriate extension, which is a requirement, use the enable_extension method in your migrations.
To use a UUID primary key without any of the extensions, set the :default option to nil:
create_table :stuffs, id: false do |t|
t.primary_key :id, :uuid, default: nil
t.uuid :foo_id
t.timestamps
end
You may also pass a custom stored procedure that returns a UUID or use a different UUID generation function from another library.
Note that setting the UUID primary key default value to nil will require you to assure that you always provide a UUID value before saving a record (as primary keys cannot be nil). This might be done via the SecureRandom.uuid method and a before_save callback, for instance.