title: How do I find out the numeric ID of the current Postgres Transaction?
body: <p>On psql I can type the following:</p>
  
  <pre><code>BEGIN;
  </code></pre>
  
  <p>what do I type to get the current id of the newly created transaction?</p>
  
  <p>I am trying to put together a demo that explains how vaccum and MVVC work in postgres. For example <code>select xmin, xmax, * from test;</code> shows the xmin and xmax of each row from the point of view of the current transaction. </p>
  
  <p>I understand the basic theory of it but want to put together an interactive exercise such that I can have two psql consoles open and then have a set of step by step instructions that show mvcc and vaccum work. </p>
  
  <p><strong>How do I get the current postgres transaction id?</strong></p>