[PIG-4790] Join after union fail due to UnionOptimizer

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.16.0
• Component/s: tez
• Hadoop Flags: Reviewed
• Assignee: Rohini Palaniswamy
• Reporter: Daniel Dai
• Created: 29/Jan/16 01:44
• Updated: 08/Jun/16 20:48
• Resolved: 10/Feb/16 18:12

Description

The following script fail to run:

rmf ooo

a = load 'student.txt' as (name:chararray, age:int, gpa:double);
b = filter a by age > 65;
c = filter a by age <=10;
d = union b, c;
e = join a by name left, d by name;
store e into 'ooo';

Exception stack:

Caused by: java.lang.IllegalArgumentException: Edge [scope-43 : org.apache.pig.backend.hadoop.executionengine.tez.runtime.PigProcessor] -> [scope-55 : org.apache.pig.backend.hadoop.executionengine.tez.runtime.PigProcessor] ({ SCATTER_GATHER : org.apache.tez.runtime.library.input.OrderedGroupedKVInput >> PERSISTED >> org.apache.tez.runtime.library.output.OrderedPartitionedKVOutput >> NullEdgeManager }) already defined!
        at org.apache.tez.dag.api.DAG.addEdge(DAG.java:272)
        at org.apache.pig.backend.hadoop.executionengine.tez.TezDagBuilder.visitTezOp(TezDagBuilder.java:311)
        at org.apache.pig.backend.hadoop.executionengine.tez.plan.TezOperator.visit(TezOperator.java:252)
        at org.apache.pig.backend.hadoop.executionengine.tez.plan.TezOperator.visit(TezOperator.java:56)
        at org.apache.pig.impl.plan.DependencyOrderWalker.walk(DependencyOrderWalker.java:87)
        at org.apache.pig.impl.plan.PlanVisitor.visit(PlanVisitor.java:46)
        at org.apache.pig.backend.hadoop.executionengine.tez.TezJobCompiler.buildDAG(TezJobCompiler.java:65)
        at org.apache.pig.backend.hadoop.executionengine.tez.TezJobCompiler.getJob(TezJobCompiler.java:111)
        ... 20 more

Disable pig.tez.opt.union the script runs fine.

Seems we shall detect this patten and disallow merge vertex group into a pair already has an edge.