title: add postgres partitioning to existing table
body: <p>All examples show:</p>
  
  <pre><code>CREATE TABLE ... PARTITION BY ...
  </code></pre>
  
  <p>Which is kind of ridiculous, because the only time you would use partitioning is when a dataset has become too large, which by definition is not going to be a new table. If someone is making a new table with partitioning, i think almost anyone would criticize that as a premature optimization. </p>