@Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result
        + ((dimensionId == null) ? 0 : dimensionId.hashCode());
    result = prime * result
        + ((dimensionType == null) ? 0 : dimensionType.hashCode());
    return result;
  }
Hive consists of a fixed, well defined set of Dimensions. Each dimension has
a type and id. Dimensions link columns in different tables
ql/src/java/org/apache/hadoop/hive/ql/metadata/Dimension.java