Composite Primary Keys and validates_uniqueness_of

This question regards the Composite Primary Keys gem
(http://compositekeys.rubyforge.org/) :

Once I use set_primary_keys, should I also use

  validates_uniqueness_of to ensure that the composite primary key is
unique and

  attr_readonly to ensure that the attributes in the primary key would
not be overwritten?

Thanks.

Learn by Doing wrote:

This question regards the Composite Primary Keys gem
(http://compositekeys.rubyforge.org/) :

Once I use set_primary_keys, should I also use

  validates_uniqueness_of to ensure that the composite primary key is
unique

You could, but remember that the DB will catch that in any case.

and

  attr_readonly to ensure that the attributes in the primary key would
not be overwritten?

Depends. If you're using a composite key, presumably it's built up from
domain data, so in many cases, you wouldn't want to make it read-only.

What is your data like that you think you need this?

Thanks.

Best,