public BucketMapJoinContext copyPartSpecMappingOnly() {
    if (bucketMapjoinContext != null &&
        bucketMapjoinContext.getBigTablePartSpecToFileMapping() != null) {
      BucketMapJoinContext context = new BucketMapJoinContext();
      context.setBigTablePartSpecToFileMapping(
          bucketMapjoinContext.getBigTablePartSpecToFileMapping());
      return context;
    }
    return null;
  }
@param aliasToFetchWork
         the aliasToFetchWork to set
ql/src/java/org/apache/hadoop/hive/ql/plan/MapredLocalWork.java