title: Update lower/upper bound of range type
body: <p>I have column of <code>tstzrange</code> type (timestamp with time zone range) and I need to update only upper or lower bound of this value (and keep inclusive/exclusive boundaries)</p>
  
  <p>I managed to change</p>
  
  <pre><code>(-infinity,infinity)
  </code></pre>
  
  <p>with</p>
  
  <pre><code>UPDATE table
  SET
      my_column = tstzrange(
          lower(my_column),
          now(),
          '()'
      )
  </code></pre>
  
  <p>and I have</p>
  
  <pre><code>(-infinity, &lt;current timestamp&gt;)
  </code></pre>
  
  <p>but I don't know how to keep boundaries from default range.. this would change even <code>[</code> <code>]</code> to <code>(</code> <code>)</code></p>