private ValidWriteIdList extractValidWriteIdList() {
    if (currDesc.getTableName() == null || !org.apache.commons.lang3.StringUtils.isBlank(currDesc.getTableName())) {
      String txnString = job.get(ValidWriteIdList.VALID_WRITEIDS_KEY);
      LOG.debug("FetchOperator get writeIdStr: " + txnString);
      return txnString == null ? new ValidReaderWriteIdList() : ValidReaderWriteIdList.fromValue(txnString);
    }
    return null;  // not fetching from a table directly but from a temp location
  }
Set context for this fetch operator in to the jobconf.
This helps InputFormats make decisions based on the scope of the complete
operation.
@param conf the configuration to modify
@param paths the list of input directories
ql/src/java/org/apache/hadoop/hive/ql/exec/FetchOperator.java