@Override public RexNode visitCall(RexCall call) {
      RexNode node = visit(call);
      if (node != null) {
        this.replaced = true;
        return node;
      }
      return super.visitCall(call);
    }
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