title: How to specify a default primary key with no auto increment
body: <pre><code>class Sizes &lt; ActiveRecord::Migration
        def self.up
          create_table :sizes do |t|
            t.integer  :size,     :null =&gt; false
          end
        end
  
        def self.down
          drop_table :sizes
        end
  end    
  
  class Sizes &lt; ActiveRecord::Migration
        def self.up
          Size.create(:id =&gt; 1, :size =&gt; 5)
          Size.create(:id =&gt; 2, :size =&gt; 10)
        end
  
        def self.down
          Size.delete_all
        end
  end
  </code></pre>
  
  <p>While trying to populate the db using the command <code>rake db:migrate</code> and i got the following output</p>
  
  <pre><code>select * from sizes;
  id          size
  1           5
  2           10
  </code></pre>
  
  <p>After I rollback the entire tables from db using the command called <code>rake db:rollback</code>. Once again I re-populated the db and now it seems to be the following </p>
  
  <pre><code>select * from sizes;
  id          size
  3           5
  4           10
  </code></pre>
  
  <p>I don't want the primary key to change, how do I stop specifying the auto increment capability or specify the ability to associate a hard-coded primary key id, so that it remains the same.</p>