[HIVE-21111] ConditionalTask cannot be cast to MapRedTask

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.1.1, 2.3.4, 3.1.1
• Fix Version/s: 4.0.0-alpha-1
• Component/s: Physical Optimizer
• Assignee: zhuwei
• Reporter: zhuwei
• Created: 09/Jan/19 06:11
• Updated: 17/Nov/22 08:55
• Resolved: 25/Mar/19 02:19

Description

We met error like this in our product environment:

java.lang.ClassCastException: org.apache.hadoop.hive.ql.exec.ConditionalTask cannot be cast to org.apache.hadoop.hive.ql.exec.mr.MapRedTask

at org.apache.hadoop.hive.ql.optimizer.physical.AbstractJoinTaskDispatcher.dispatch(AbstractJoinTaskDispatcher.java:173)

 

There is a bug in function org.apache.hadoop.hive.ql.optimizer.physical.AbstractJoinTaskDispatcher.dispatch:

if (tsk.isMapRedTask())

{ Task<? extends Serializable> newTask = this.processCurrentTask((MapRedTask) tsk, ((ConditionalTask) currTask), physicalContext.getContext()); walkerCtx.addToDispatchList(newTask); }

In the above code, when tsk is instance of ConditionalTask, tsk.isMapRedTask() still can be true, but it cannot be cast to MapRedTask.

Issue Links

• is fixed by: HIVE-14557 Nullpointer When both SkewJoin and Mapjoin Enabled