Hive执行SQL语句

• org.apache.hadoop.hive.ql.Driver类
• public int execute(boolean deferClose) 方法

1. 从Plan中统计MR/Tez/Spark Task数量

        int mrJobs = Utilities.getMRTasks(plan.getRootTasks()).size();
      int jobs = mrJobs
        + Utilities.getTezTasks(plan.getRootTasks()).size()
        + Utilities.getSparkTasks(plan.getRootTasks()).size();

2. DriverContext在TaskRunner线程中启动任务。

      DriverContext driverCxt = new DriverContext(ctx);
      driverCxt.prepare(plan);

      ctx.setHDFSCleanup(true);
      this.driverCxt = driverCxt; // for canceling the query (should be bound to session?)

      // Add root Tasks to runnable
      for (Task tsk : plan.getRootTasks()) {
        // This should never happen, if it does, it's a bug with the potential to produce
        // incorrect results.
        assert tsk.getParentTasks() == null || tsk.getParentTasks().isEmpty();
        driverCxt.addToRunnable(tsk);

        Metrics metrics = MetricsFactory.getInstance();
        if (metrics != null) {
          tsk.updateTaskMetrics(metrics);
        }
      }

      // poll the Tasks to see which one completed
        TaskRunner tskRun = driverCxt.pollFinished();
        if (tskRun == null) {
          continue;
        }
        hookContext.addCompleteTask(tskRun);
        queryDisplay.setTaskResult(tskRun.getTask().getId(), tskRun.getTaskResult());

        Task tsk = tskRun.getTask();
        TaskResult result = tskRun.getTaskResult();

        int exitVal = result.getExitVal();
        if (isInterrupted()) {
          return handleInterruption("when checking the execution result.");
        }
        if (exitVal != 0) {
          if (tsk.ifRetryCmdWhenFail()) {
            driverCxt.shutdown();
            // in case we decided to run everything in local mode, restore the
            // the jobtracker setting to its initial value
            ctx.restoreOriginalTracker();
            throw new CommandNeedRetryException();
          }
          Task backupTask = tsk.getAndInitBackupTask();
          if (backupTask != null) {
            setErrorMsgAndDetail(exitVal, result.getTaskError(), tsk);
            console.printError(errorMessage);
            errorMessage = "ATTEMPT: Execute BackupTask: " + backupTask.getClass().getName();
            console.printError(errorMessage);

            // add backup task to runnable
            if (DriverContext.isLaunchable(backupTask)) {
              driverCxt.addToRunnable(backupTask);
            }
            continue;

          } else {
            setErrorMsgAndDetail(exitVal, result.getTaskError(), tsk);
            invokeFailureHooks(perfLogger, hookContext,
              errorMessage + Strings.nullToEmpty(tsk.getDiagnosticsMessage()), result.getTaskError());
            SQLState = "08S01";
            console.printError(errorMessage);
            driverCxt.shutdown();
            // in case we decided to run everything in local mode, restore the
            // the jobtracker setting to its initial value
            ctx.restoreOriginalTracker();
            return exitVal;
          }
        }

        driverCxt.finished(tskRun);

启动任务：

 private TaskRunner launchTask(Task tsk, String queryId, boolean noName,
      String jobname, int jobs, DriverContext cxt) throws HiveException {
      ……
    tsk.initialize(queryState, plan, cxt, ctx.getOpContext());
    TaskResult tskRes = new TaskResult();
    TaskRunner tskRun = new TaskRunner(tsk, tskRes);

3. 释放Plan

releasePlan(plan);