private static boolean isColumnExpr(RexNode node) {
      return !node.getType().isStruct() && !HiveCalciteUtil.getInputRefs(node).isEmpty()
          && HiveCalciteUtil.isDeterministic(node);
    }
Interprets argument as a constraint; if not possible returns null.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HivePointLookupOptimizerRule.java