title: How dynamic-update=true works internally in hibernate?
body: <p>So I understand what setting this attribute <strong>dynamic-update=true</strong> does, i.e it considers only those fields that were modified and omits the job of setting null values for other fields. <em>Saving an overhead, good on performance.</em> </p>
  
  <p>Asking out of curiosity: How does hibernate come to know what all fields were modified? Does it do a comparison of the result generated by the select query to the database first before firing an update query? Assuming yes, then isn't comparison an overhead to performance?</p>
  
  <p>Correct me if I'm wrong. Thanks in advance!</p>