@Override public boolean equals(final Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }
      final RowKey rowKey = (RowKey) o;
      return hashCode == rowKey.hashCode
              && Objects.equals(keys, rowKey.keys);
    }
Identifies a calcite row (as in relational algebra)
criteria/elasticsearch/src/org/immutables/criteria/elasticsearch/Json.java