protected void defineColumns(StringBuilder query) {
    if (sourceTab != null) {
      query.append("(")
          .append("`operation` int, `originalTransaction` bigint, `bucket` int, `rowId` bigint, `currentTransaction` bigint, ")
          .append("`row` struct<")
          .append(StringUtils.join(getColumnDescs(), ','))
          .append(">) ");
    }
  }
Define columns of the create query.
ql/src/java/org/apache/hadoop/hive/ql/txn/compactor/CompactionQueryBuilder.java