title: How to query PostgreSQL for all records where hstore is empty?
body: <p>I would like to query my PostgreSQL table for all rows that have an empty hstore. It must be obvious to all but me, as I can't find any documentation on how to do it nor other StackOverflow questions answering the question. Checking for NULL isn't helpful, as I get back all rows, even those rows where <code>properties</code> has no keys/values:</p>
  
  <pre><code>SELECT widgets.* 
  FROM "widgets" 
  WHERE properties IS NOT NULL
  </code></pre>
  
  <p>Any ideas how to do this?</p>