private void cleanupGraceHashJoin() {
    for (byte pos = 0; pos < mapJoinTables.length; pos++) {
      if (pos != conf.getPosBigTable()) {
        LOG.info("Cleaning up small table data at pos: " + pos);
        HybridHashTableContainer container = (HybridHashTableContainer) mapJoinTables[pos];
        container.clear();
      }
    }
  }
Clean up data participating the join, i.e. in-mem and on-disk files for small table(s) and big table
ql/src/java/org/apache/hadoop/hive/ql/exec/MapJoinOperator.java