@Override public RexNode visitInputRef(RexInputRef inputRef) {
      RexNode node = visit(inputRef);
      if (node == null) {
        return super.visitInputRef(inputRef);
      }
      this.replaced = true;
      return node;
    }
Planner rule that infers constant expressions from Filter into
a Project operator.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveProjectFilterPullUpConstantsRule.java