private int executeTask(Context generalContext, Task<?> task) {
    TaskQueue taskQueue = new TaskQueue();
    task.initialize(context.getQueryState(), context.getQueryPlan(), taskQueue, generalContext);
    int ret = task.execute();
    if (task.getException() != null) {
      context.getTask().setException(task.getException());
    }
    return ret;
  }
Operation process of concatenating the files of a table/partition.
ql/src/java/org/apache/hadoop/hive/ql/ddl/table/storage/concatenate/AlterTableConcatenateOperation.java