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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.
# File activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb, line 44 def primary_key(name, type = :primary_key, **options) options[:auto_increment] = true if [:integer, :bigint].include?(type) && !options.key?(:default) if type == :uuid options[:default] = options.fetch(:default, "gen_random_uuid()") elsif options.delete(:auto_increment) == true && %(integer bigint).include?(type) type = if type == :bigint || options[:limit] == 8 :bigserial else :serial end end super end