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https://issues.apache.org/jira/browse/PIG-1327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12849995#action_12849995
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Ankur commented on PIG-1327:
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Yes, I verified that
> Incorrect column pruning after multiple JOIN operations
> -------------------------------------------------------
>
> Key: PIG-1327
> URL: https://issues.apache.org/jira/browse/PIG-1327
> Project: Pig
> Issue Type: Bug
> Affects Versions: 0.6.0
> Reporter: Ankur
>
> In a script with multiple JOIN and GROUP operations, the column pruner
> incorrectly removes some of the fields that it shouldn't. Here is a script
> that demonstrates the issue
> = LOAD 'data1' USING PigStorage() AS (a:chararray, b:chararray, c:long);
> B = LOAD 'data2' USING PigStorage() AS (x:chararray, y:chararray, z:long);
> C = LOAD 'data3' using PigStorage() AS (d:chararray, e:chararray,
> f:chararray);
> join1 = JOIN B by x, A by a;
> filtered1 = FILTER join1 BY y == b;
> InterimData = FOREACH filtered1 GENERATE a, b, c, y, z;
> join2 = JOIN InterimData BY b LEFT OUTER, C BY d PARALLEL 2;
> proj = FOREACH join2 GENERATE a,b,y,z,e,f;
> TopNPrj = FOREACH proj GENERATE a, (( e is not null and e != '') ? e :
> 'None') , z;
> TopNDataGrp = GROUP TopNPrj BY (a, e) PARALLEL 2;
> TopNDataSum = FOREACH TopNDataGrp GENERATE flatten(group) as (a, e),
> SUM(TopNPrj.z) as views;
> TopNDataRegrp = GROUP TopNDataSum BY (a) PARALLEL 2;
> TopNDataCount = FOREACH TopNDataRegrp { OrderedData = ORDER TopNDataSum BY
> views desc; LimitedData = LIMIT OrderedData 50; GENERATE LimitedData; }
> TopNData = FOREACH TopNDataCount GENERATE flatten($0) as (a, e, views);
> store TopNData into 'tmpTopN';
> TopNData_stored = load 'tmpTopN' as (a:chararray, b:chararray, c:long);
> joinTopNData = JOIN TopNData_stored BY (a,b) RIGHT OUTER, proj BY (a,b)
> PARALLEL 2;
> describe joinTopNData;
> STORE joinTopNData INTO 'output';
> The column 'f' from relation 'C' participating in the 2nd JOIN is missing
> from the final join ouput
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