@Override
  public boolean equals(Object o) {
    if (super.equals(o)) {
      return true;
    }
    if (o == null) {
      return false;
    }
    if (o instanceof Dimension) {
      Dimension d = (Dimension) o;
      return (dimensionId.equals(d.dimensionId) && (dimensionType == d.dimensionType));
    }
    return false;
  }
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