@Override
    public boolean equals(Object other) {
      if ((other == null) || !(other instanceof Key)) {
        return false;
      }
      Key that = (Key) other;
      return catName.equals(that.catName) && dbName.equals(that.dbName) &&
          tblName.equals(that.tblName) && colName.equals(that.colName);
    }
Key object for the stats cache hashtable
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/AggregateStatsCache.java