public static HashTableLoader getLoader(Configuration hconf) {
    if (HiveConf.getVar(hconf, ConfVars.HIVE_EXECUTION_ENGINE).equals("tez")) {
      return new org.apache.hadoop.hive.ql.exec.tez.HashTableLoader();
    } else {
      return new org.apache.hadoop.hive.ql.exec.mr.HashTableLoader();
    }
  }
HashTableLoaderFactory is used to determine the strategy
of loading the hashtables for the MapJoinOperator
ql/src/java/org/apache/hadoop/hive/ql/HashTableLoaderFactory.java