code: public String[] getPartitionKeys(String location, Job job) throws IOException
      {
          if (!usePartitionFilter)
              return null;
          List<ColumnDef> indexes = getIndexes();
          String[] partitionKeys = new String[indexes.size()];
          for (int i = 0; i < indexes.size(); i++)
          {
              partitionKeys[i] = new String(indexes.get(i).getName());
          }
          return partitionKeys;
      }
docs: return partition keys