[jira] Commented: (PIG-1169) Top-N queries produce incorrect results when a store statement is added between order by and limit statement

["Richard Ding (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PIG-1169?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12794466#action_12794466 ] 

Richard Ding commented on PIG-1169:
-----------------------------------

In this case, a workaroud is to disable the multi-query optimization (use command line option -M).

> Top-N queries produce incorrect results when a store statement is added between order by and limit statement
> ------------------------------------------------------------------------------------------------------------
>
>                 Key: PIG-1169
>                 URL: https://issues.apache.org/jira/browse/PIG-1169
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>    Affects Versions: 0.7.0
>            Reporter: Richard Ding
>            Assignee: Richard Ding
>
> ??We tried to get top N results after a groupby and sort, and got different results with or without storing the full sorted results. Here is a skeleton of our pig script.??
> {code}
> raw_data = Load '<input_files>' AS (f1, f2, ..., fn);
> grouped = group raw_data by (f1, f2);
> data = foreach grouped generate FLATTEN(group). SUM(raw_data.fk) as value;
> ordered = order data by value DESC parallel 10;
> topn = limit ordered 10;
> store ordered into 'outputdir/full';
> store topn into 'outputdir/topn';
> {code}
> ??With the statement 'store ordered ...', top N results are incorrect, but without the statement, results are correct. Has anyone seen this before? I know a similar bug has been fixed in the multi-query release. We are on pig .4 and hadoop .20.1.??

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