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From "william zhu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HIVE-6831) The job schedule in condition task could not be correct with skewed join optimization
Date Thu, 03 Apr 2014 10:07:15 GMT
william zhu created HIVE-6831:
---------------------------------

             Summary: The job schedule in condition task could not be correct with skewed
join optimization
                 Key: HIVE-6831
                 URL: https://issues.apache.org/jira/browse/HIVE-6831
             Project: Hive
          Issue Type: Bug
          Components: Query Processor
    Affects Versions: 0.11.0
         Environment: Hive 0.11.0
            Reporter: william zhu


Code isnippet in ConditionalTask.java we can see : 

    // resolved task
        if (driverContext.addToRunnable(tsk)) {
          console.printInfo(tsk.getId() + " is selected by condition resolver.");
    }

The selected task be added into the runnable queue immediately without any dependency checking.
If the selected task is original task ,and its parent task is not being executed, then the
result will be incorrect.

Like this:
1. Before skew join optimization:
Step1 ,Step 2 <-- step 3   ( Step1 and Step2 is Step 3's parent)
2. after skew join optimization:
Step1 <- Step4 (ConditionTask)<- consists of [Step3,Step10]    
Step2 <- Step5 (ConditionTask)<- consists of [Step3,Step11]
3. Runing
Step3 is selected in Step4 and Step5
Step3 will be execute immediately after Step4 , its not correct.
Step3 will be execute after Step5 again, its not correct either.
4. The correct scheduler is that step3 will be execute after step4 and step5.
5. So, I add a checking operate in the snippet  as bellow:

        if (!driverContext.getRunnable().contains(tsk)) {
          console.printInfo(tsk.getId() + " is selected by condition resolver.");
          if(DriverContext.isLaunchable(tsk)){
        	 // run the original task now
        	  driverContext.addToRunnable(tsk);
          }
        }

So , that is work right for me in my enviroment. I am not sure whether it will has some problems
 in someother condition. 






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