title: Does Solr data import handler support custom variables?
body: <p>I currently have an issue with my data import handler where <code>${dataimporter.last_index_time}</code> is not granular enough to capture two events that happen within a second of each other, leading to issues where a record is skipped over in my database.</p>
  
  <p>I am thinking to replace <code>last_index_time</code> with a simple atomically incrementing value as opposed to a datetime, but in order to do that I need to be able to set and read custom variables through solr that can be referenced in my <code>data-config.xml</code> file.</p>
  
  <p><strong>Alternatively</strong>, if I could find some way to <em>set</em> <code>dataimporter.last_index_time</code>, that would work just as well as I could ensure that the last_index_time is less than the newly-committed rows (and more importantly, that it is set from the same clock).</p>
  
  <p>Does Solr support this?</p>