/**
  * Creates a new SargFactory.
  *
  * @param rexBuilder factory for instances of {@link RexNode}, needed internally in the sarg
  *     representation, and also for recomposing sargs into equivalent rex trees
  */
 public SargFactory(RexBuilder rexBuilder) {
   this.rexBuilder = rexBuilder;
   rexNull = rexBuilder.constantNull();
 }