title: PostgreSQL: add_column "after" option usage in Rails migration
body: <p>I'm trying to add a new column, 'latitude', to an existing Postgres table, after the 'location' column.</p>
  
  <p>Using this syntax puts the column in the correct place:</p>
  
  <pre><code>add_column :table, :column, :decimal, :after =&gt; :existing_column
  </code></pre>
  
  <p>And using this syntax ensures that the field is the correct data type</p>
  
  <pre><code>add_column :table, :column, :decimal, {:precision =&gt; 10, :scale =&gt; 6}
  </code></pre>
  
  <p>But when I try and combine the two:</p>
  
  <pre><code>add_column :table, :column, :decimal, {:precision =&gt; 10, :scale =&gt; 6}, :after =&gt; :existing_column
  </code></pre>
  
  <p>I get "ArgumentError: wrong number of arguments (5 for 3..4)"</p>
  
  <p>"Not to worry", I thought, "I'll just combine the arguements!":</p>
  
  <pre><code>add_column :table, :column, :decimal, {:precision =&gt; 10, :scale =&gt; 6, :after =&gt; :existing_column}
  </code></pre>
  
  <p>But then the columns appear at the end of the table. What am I doing wrong?</p>
  
  <p>Thanks :)</p>