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Date: Thu, 31 Oct 2013 01:56:25 +0000 (UTC)
From: "Sergey Shelukhin (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
Message-ID: <JIRA.12675918.1382750706162.9075.1383184585578@arcas>
In-Reply-To: <JIRA.12675918.1382750706162@arcas>
References: <JIRA.12675918.1382750706162@arcas>
Subject: [jira] [Commented] (HIVE-5657) TopN produces incorrect results with
 count(distinct)
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    [ https://issues.apache.org/jira/browse/HIVE-5657?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13809846#comment-13809846 ] 

Sergey Shelukhin commented on HIVE-5657:
----------------------------------------

but the hash for distinct in the review always returns FORWARD in current patch on FB:
{code}
class HashForDistinct extends HashForGroup {

 HashForDistinct(int topN, long threshold, BinaryCollector collector) {
 super(topN, threshold, collector);
 }

 @Override
 protected int index(int index) {
 return FORWARD;
 }
}
{code}

> TopN produces incorrect results with count(distinct)
> ----------------------------------------------------
>
>                 Key: HIVE-5657
>                 URL: https://issues.apache.org/jira/browse/HIVE-5657
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Sergey Shelukhin
>            Assignee: Navis
>            Priority: Critical
>         Attachments: D13797.1.patch, example.patch, HIVE-5657.1.patch.txt
>
>
> Attached patch illustrates the problem.
> limit_pushdown test has various other cases of aggregations and distincts, incl. count-distinct, that work correctly (that said, src dataset is bad for testing these things because every count, for example, produces one record only), so something must be special about this.
> I am not very familiar with distinct- code and these nuances; if someone knows a quick fix feel free to take this, otherwise I will probably start looking next week. 


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