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https://issues.apache.org/jira/browse/PIG-3938?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14039214#comment-14039214
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Daniel Dai commented on PIG-3938:
---------------------------------
Reading through the comments, it seems the issue is because MapToBag does not
define the right schema, so cast fail? We shall define schema in MapToBag since
the default is just bag with no inner schema.
> Type cast doesn't work after flatten result of UDF
> --------------------------------------------------
>
> Key: PIG-3938
> URL: https://issues.apache.org/jira/browse/PIG-3938
> Project: Pig
> Issue Type: Bug
> Components: internal-udfs
> Affects Versions: 0.12.0, 0.11.1
> Reporter: Hongchang Li
>
> this ticket was very close to
> http://stackoverflow.com/questions/8828839/how-can-correct-data-types-on-apache-pig-be-enforced.
> To reproduce the issue, first, we have an UDF to cast map to bag, code almost
> like(http://stackoverflow.com/questions/12476929/group-key-value-of-map-in-pig?answertab=votes#tab-top)
> {code:title=test.pig}
> $ cat test.pig
> register polisan/maptobag.jar;
> define MAPTOBAG maptobag.MAPTOBAG();
> A = load 'polisan/input1.txt' using PigStorage(' ') as (id:chararray, kv:[]);
> B = foreach A generate id, MAPTOBAG(kv) as to_bag;
> C = foreach B generate id, flatten(to_bag) as (key:chararray,
> value:chararray);
> D = group C by (id, key);
> E = foreach D generate group, MIN(C.value);
> dump E;
> {code}
> {code:title=polisan/input1.pig}
> 1 [x#1,y#ab]
> 1 [x#2,y#cd]
> {code}
> then run the pig, I got exception as following:
> {noformat}
> 2014-05-15 19:44:52,944 [Thread-2] WARN
> org.apache.hadoop.mapred.LocalJobRunner - job_local_0001
> org.apache.pig.backend.executionengine.ExecException: ERROR 0: Exception
> while executing (Name: D: Local Rearrange[tuple]{tuple}(false) - scope-42
> Operator Key: scope-42):
> org.apache.pig.backend.executionengine.ExecException: ERROR 2106: Error while
> computing min in Initial
> at
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.processInput(PhysicalOperator.java:289)
> at
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POLocalRearrange.getNextTuple(POLocalRearrange.java:263)
> at
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.runPipeline(PigGenericMapBase.java:282)
> at
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.map(PigGenericMapBase.java:277)
> at
> org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.map(PigGenericMapBase.java:1)
> at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
> at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:764)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:370)
> at
> org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:212)
> Caused by: org.apache.pig.backend.executionengine.ExecException: ERROR 2106:
> Error while computing min in Initial
> at org.apache.pig.builtin.StringMin$Initial.exec(StringMin.java:81)
> at org.apache.pig.builtin.StringMin$Initial.exec(StringMin.java:1)
> at
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:352)
> at
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNextTuple(POUserFunc.java:391)
> at
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.getNext(PhysicalOperator.java:334)
> at
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.processPlan(POForEach.java:378)
> at
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.getNextTuple(POForEach.java:298)
> at
> org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.processInput(PhysicalOperator.java:281)
> ... 8 more
> Caused by: java.lang.ClassCastException: org.apache.pig.data.DataByteArray
> cannot be cast to java.lang.String
> at org.apache.pig.builtin.StringMin$Initial.exec(StringMin.java:73)
> ... 15 more
> {noformat}
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