protected ValidReaderWriteIdList getValidCleanerWriteIdList(CompactionInfo info, ValidTxnList validTxnList)
          throws NoSuchTxnException, MetaException {
    List<String> tblNames = Collections.singletonList(AcidUtils.getFullTableName(info.dbname, info.tableName));
    GetValidWriteIdsRequest request = new GetValidWriteIdsRequest(tblNames);
    request.setValidTxnList(validTxnList.writeToString());
    GetValidWriteIdsResponse rsp = txnHandler.getValidWriteIds(request);
    // we could have no write IDs for a table if it was never written to but
    // since we are in the Cleaner phase of compactions, there must have
    // been some delta/base dirs
    assert rsp != null && rsp.getTblValidWriteIdsSize() == 1;

    return new ValidCleanerWriteIdList(
        TxnCommonUtils.createValidReaderWriteIdList(rsp.getTblValidWriteIds().get(0)));
  }
An abstract class which defines the list of utility methods for performing cleanup activities.
ql/src/java/org/apache/hadoop/hive/ql/txn/compactor/handler/TaskHandler.java