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From "Benjamin Reed (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-812) COUNT(*) does not work
Date Wed, 19 Aug 2009 04:05:14 GMT

    [ https://issues.apache.org/jira/browse/PIG-812?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12744868#action_12744868
] 

Benjamin Reed commented on PIG-812:
-----------------------------------

@olga
1) can you suggest some text, i'm not a sql guru
2) this patch is focused on documenting * and flatten. i didn't really change the documentation
for boolean, tuple, field, and general expression
3) you are saying that i should have 'key' in the description correct?
4) i don't think that is a typo. it is a tuple with one field that is a bag of tuples, when
you flatten the bag field the individual tuples will pop out. can you suggest how to make
it more clear?
5) it's easy enough to switch around, but it seemed that group was the more general term (if
such a term could be used since they are aliases of each other :) where cogroup implies more
than one. don't you think?

> COUNT(*) does not work 
> -----------------------
>
>                 Key: PIG-812
>                 URL: https://issues.apache.org/jira/browse/PIG-812
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>    Affects Versions: 0.2.0
>            Reporter: Viraj Bhat
>            Assignee: Benjamin Reed
>             Fix For: 0.2.0
>
>         Attachments: PIG-812.patch, PIG-812.patch, PIG-812.pdf, studenttab10k
>
>
> 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)
> ================================================================

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