[jira] Updated: (PIG-813) Semantics of * and count

["George Mavromatis (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/PIG-813?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

George Mavromatis updated PIG-813:
----------------------------------

    Component/s:     (was: impl)
                 documentation
       Priority: Major  (was: Critical)
    Description: 
Continuation of PIG-812. See PIG-812 for more details.


In order for this to be resolved in the right manner the following must added in the http://hadoop.apache.org/pig/docs/r0.2.0/piglatin.html

1) The semantics of * as explained by Olga.
2) An example of GROUP ALL

Otherwise people will waste their time doing the same (documentation-caused) mistakes again.

  was:
Pig script to count the number of rows in a studenttab10k file which contains 10k records.
{code}
studenttab = LOAD 'studenttab10k' AS (name:chararray, age:int,gpa:float);

X2 = GROUP studenttab ALL;

describe X2;

Y2 = FOREACH X2 GENERATE COUNT(*);

explain Y2;

DUMP Y2;

{code}

returns the following error
================================================================
ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1066: Unable to open iterator for alias Y2
Details at logfile: /homes/viraj/pig-svn/trunk/pig_1242783700970.log
================================================================

If you look at the log file:
================================================================
Caused by: java.lang.ClassCastException
        at org.apache.pig.builtin.COUNT$Initial.exec(COUNT.java:76)
        at org.apache.pig.builtin.COUNT$Initial.exec(COUNT.java:68)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:201)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:235)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.processPlan(POForEach.java:254)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.getNext(POForEach.java:204)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.processInput(PhysicalOperator.java:231)
        at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POLocalRearrange.getNext(POLocalRearrange.java:223)
        at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.runPipeline(PigMapBase.java:245)
        at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.map(PigMapBase.java:236)
        at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapReduce$Map.map(PigMapReduce.java:88)
        at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:47)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:227)
================================================================


> Semantics of * and count
> ------------------------
>
>                 Key: PIG-813
>                 URL: https://issues.apache.org/jira/browse/PIG-813
>             Project: Pig
>          Issue Type: Bug
>          Components: documentation
>    Affects Versions: 0.2.0
>            Reporter: George Mavromatis
>             Fix For: 0.2.0
>
>
> Continuation of PIG-812. See PIG-812 for more details.
> In order for this to be resolved in the right manner the following must added in the http://hadoop.apache.org/pig/docs/r0.2.0/piglatin.html
> 1) The semantics of * as explained by Olga.
> 2) An example of GROUP ALL
> Otherwise people will waste their time doing the same (documentation-caused) mistakes again.

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