title: Duplicate ID's being generated violating primary key contraints
body: <p>Can anyone help explain this? I am using the Populator and Faker gems to put some generated data into my database. Among other things, I generate 10,000 comments (which are from the 'acts_as_commentable' gem. All this works. However, when I go to add a new comment, I get an error saying that I am violating the primary key by using an existing id. Look at my console output below. You can see I have 10,000 records starting with ID 1 and ending with ID 100000. I then try to add a new comment and it fails. This is only happening with this model/table. I can add new users, etc.    </p>
  
  <pre><code>&gt;&gt; Comment.first(:order =&gt; 'id').id
  =&gt; 1
  &gt;&gt; Comment.last(:order =&gt; 'id').id
  =&gt; 10000
  &gt;&gt; Comment.count
  =&gt; 10000
  &gt;&gt; Comment.create(:title =&gt; 'wtf is up?')
  ActiveRecord::RecordNotUnique: PGError: ERROR:  duplicate key value violates unique constraint "comments_pkey"
  DETAIL:  Key (id)=(1) already exists.
  </code></pre>
  
  <p>I suspect this is related to how the Populator gem is batching the records into the database. It is only happening on models/tables that I see with Populator.</p>