public List<RexNode> getValuesInOrder(List<RexNodeRef> columns) throws SemanticException {
        List<RexNode> ret = new ArrayList<>();
        for (RexNodeRef rexInputRef : columns) {
          Constraint constraint = constraints.get(rexInputRef);
          if (constraint == null) {
            throw new SemanticException("Unable to find constraint which was earlier added.");
          }
          ret.add(constraint.constNode);
        }
        return ret;
      }
A group of Constraints.

Examples:
 (a=1 && b=1)
 (a=1)

Note: any rexNode is accepted as constraint; but it might be keyed with the empty key;
which means it can't be parsed as a constraint for some reason; but for completeness...
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HivePointLookupOptimizerRule.java