CompiledValue getKey(ExecutionContext context)
      throws AmbiguousNameException, TypeMismatchException {
    return getPathAndKey(context)._key;
  }
@return true if the index is a MapIndex of type allkeys ([*]) and this is a != comparison
        or it is comparing the map value against null
geode-core/src/main/java/org/apache/geode/cache/query/internal/CompiledComparison.java