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https://issues.apache.org/jira/browse/PIG-2137?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13053577#comment-13053577
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Dmitriy V. Ryaboy commented on PIG-2137:
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Thanks
I'll commit PIG-2137.1 to 0.8, 0.9, and trunk.
> SAMPLE should not be pushed above DISTINCT
> ------------------------------------------
>
> Key: PIG-2137
> URL: https://issues.apache.org/jira/browse/PIG-2137
> Project: Pig
> Issue Type: Bug
> Affects Versions: 0.8.0, 0.8.1, 0.9.0, 0.10
> Reporter: Dmitriy V. Ryaboy
> Assignee: Dmitriy V. Ryaboy
> Priority: Critical
> Attachments: PIG-2137.1.patch, PIG-2137.patch
>
>
> I have an input file that contains 50,000 distinct integers. Each integer is
> repeated twice, for a total of 100,000 lines.
> Script 1, using GROUP BY to get distinct entries in the data, works:
> {code}
> grunt> f = load 'tmp/dupnumbers.txt';
> grunt> d = foreach (group f by $0) generate group;
> grunt> s = sample d 0.01;
> grunt> n = foreach (group s all) generate COUNT(s);
> grunt> dump n;
> (493)
> {code}
> Script 2, using DISTINCT for the same purpose, allows sampling to be done
> before DISTINCT:
> {code}
> grunt> f = load 'tmp/dupnumbers.txt';
> grunt> d = distinct f;
> grunt> s = sample d 0.01;
> grunt> n = foreach (group s all) generate COUNT(s);
> (980)
> {code}
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