[PIG-2119] DuplicateForEachColumnRewrite makes assumptions about the position of LOGGenerate in the plan

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.9.0, 0.9.1
• Fix Version/s: 0.9.2, 0.10.0, 0.11
• Hadoop Flags: Reviewed
• Assignee: Daniel Dai
• Reporter: Gianmarco De Francisci Morales
• Created: 12/Jun/11 12:17
• Updated: 23/Jan/12 07:31
• Resolved: 02/Nov/11 06:19

Description

The input:

grunt> cat b.txt
a       11
b       3
c       10
a       12
b       10
c       15

The script:

a = load 'b.txt' AS (id:chararray, num:int);
b = group a by id;
c = foreach b { 
  d = order a by num DESC;
  n = COUNT(a);
  e = limit d 1;
  generate n;
}

The exception:

Caused by: java.lang.ClassCastException: org.apache.pig.newplan.logical.relational.LOLimit cannot be cast to org.apache.pig.newplan.logical.relational.LOGenerate
        at org.apache.pig.newplan.logical.rules.DuplicateForEachColumnRewrite$DuplicateForEachColumnRewriteTransformer.check(DuplicateForEachColumnRewrite.java:87)
        at org.apache.pig.newplan.optimizer.PlanOptimizer.optimize(PlanOptimizer.java:108)

I know the script is a bit pointless, but I was just testing and modifying the script bit by bit.
If I remove the limit in any case I get the same exception but with LOSort.

The problem, I think, is that the rule assumes there is only 1 sink in the nested block and that this sink is a LOGenerate.