[jira] [Assigned] (HIVE-22294) ConditionalWork cannot be cast to MapredWork When both skew.join and auto.convert is on.

["Qiang.Kang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-22294?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Qiang.Kang reassigned HIVE-22294:
---------------------------------

    Assignee: Rui Li

> ConditionalWork cannot be cast to MapredWork  When both skew.join and auto.convert is on.  
> -------------------------------------------------------------------------------------------
>
>                 Key: HIVE-22294
>                 URL: https://issues.apache.org/jira/browse/HIVE-22294
>             Project: Hive
>          Issue Type: Bug
>          Components: Physical Optimizer
>    Affects Versions: 2.3.0, 3.1.1, 2.3.4
>            Reporter: Qiang.Kang
>            Assignee: Rui Li
>            Priority: Critical
>
> Our hive version is 1.2.1 which has merged some patches (including patches mentioned  in https://issues.apache.org/jira/browse/HIVE-14557, https://issues.apache.org/jira/browse/HIVE-16155 ) .
>  
> My sql query string is like this:
> ```
> set hive.auto.convert.join = true;
> set hive.optimize.skewjoin=true;
>  
> SELECT a.*
> FROM
> a
> JOIN b
> ON a.id=b.id AND a.uid = b.uid 
> LEFT JOIN c
> ON b.id=c.id AND b.uid=c.uid;
> ```
> And we met some error: 
> FAILED: ClassCastException org.apache.hadoop.hive.ql.plan.ConditionalWork cannot be cast to org.apache.hadoop.hive.ql.plan.MapredWork
>  
> The main reason is that there is a conditional task (*MapJoin*) in the list tasks of another Conditional task (*SkewJoin*).  Here is the code snippet where it throws this exception:
> `org.apache.hadoop.hive.ql.optimizer.physical.MapJoinResolver:`
> ```java
> public Object dispatch(Node nd, Stack<Node> stack, Object... nodeOutputs)
>  throws SemanticException {
>  Task<? extends Serializable> currTask = (Task<? extends Serializable>) nd;
>  // not map reduce task or not conditional task, just skip
>  if (currTask.isMapRedTask()) {
>  if (currTask instanceof ConditionalTask) {
>  // get the list of task
>  List<Task<? extends Serializable>> taskList = ((ConditionalTask) currTask).getListTasks();
>  for (Task<? extends Serializable> tsk : taskList) {
>  if (tsk.isMapRedTask()) {
>  
> //  ATTENTION: tsk May be ConditionalTask !!!
>  this.processCurrentTask(tsk, ((ConditionalTask) currTask));
>  }
>  }
>  } else {
>  this.processCurrentTask(currTask, null);
>  }
>  }
>  return null;
> }
> private void processCurrentTask(Task<? extends Serializable> currTask,
>  ConditionalTask conditionalTask) throws SemanticException {
>  // get current mapred work and its local work
>  MapredWork mapredWork = (MapredWork) currTask.getWork(); // WRONG!!!!!!
>  MapredLocalWork localwork = mapredWork.getMapWork().getMapRedLocalWork();
> ```
>  
> Here is some detail Information about query plan:
> *-  set hive.auto.convert.join = true; set hive.optimize.skewjoin=false;*
> ```
> Stage-1 is a root stage [a join b]
>  Stage-12 [map join]depends on stages: Stage-1 , consists of Stage-13, Stage-2
>  Stage-13 has a backup stage: Stage-2
>  Stage-11 depends on stages: Stage-13
>  Stage-8 depends on stages: Stage-2, Stage-11 , consists of Stage-5, Stage-4, Stage-6
>  Stage-5
>  Stage-0 depends on stages: Stage-5, Stage-4, Stage-7
>  Stage-14 depends on stages: Stage-0
>  Stage-3 depends on stages: Stage-14
>  Stage-4
>  Stage-6
>  Stage-7 depends on stages: Stage-6
>  Stage-2
> ```
> *-  set hive.auto.convert.join = false; set hive.optimize.skewjoin=true;*
> ```
> STAGE DEPENDENCIES:
>  Stage-1 is a root stage
>  Stage-12 depends on stages: Stage-1 , consists of Stage-13, Stage-2
>  Stage-13 [skew Join map local task]
>  Stage-11 depends on stages: Stage-13
>  Stage-2 depends on stages: Stage-11
>  Stage-8 depends on stages: Stage-2 , consists of Stage-5, Stage-4, Stage-6
>  Stage-5
>  Stage-0 depends on stages: Stage-5, Stage-4, Stage-7
>  Stage-14 depends on stages: Stage-0
>  Stage-3 depends on stages: Stage-14
>  Stage-4
>  Stage-6
>  Stage-7 depends on stages: Stage-6
> ```
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