private void writeDelay(){
  try {
    Thread.sleep(10);
  }
 catch (  InterruptedException e) {
    fail("Interrupted sleep.");
  }
}

private void writeDelay ( ) { try { Thread . sleep ( 10 ) ; } catch ( InterruptedException e ) { fail ( "Interrupted sleep." ) ; } }
a very slight delay to ensure that successive groups of queries in the db cannot have the same timestamp .
