Mailing-List: contact dev-help@hive.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@hive.apache.org
Date: Wed, 4 May 2011 02:16:03 +0000 (UTC)
From: "Siying Dong (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
Message-ID: 
 <468477287.20530.1304475363374.JavaMail.tomcat@hel.zones.apache.org>
In-Reply-To: 
 <41466411.17154.1304386023239.JavaMail.tomcat@hel.zones.apache.org>
Subject: [jira] [Updated] (HIVE-2146) Block Sampling should adjust number of
 reducers accordingly to make it useful
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


     [ https://issues.apache.org/jira/browse/HIVE-2146?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Siying Dong updated HIVE-2146:
------------------------------

    Status: Patch Available  (was: Open)

> Block Sampling should adjust number of reducers accordingly to make it useful
> -----------------------------------------------------------------------------
>
>                 Key: HIVE-2146
>                 URL: https://issues.apache.org/jira/browse/HIVE-2146
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Siying Dong
>            Assignee: Siying Dong
>         Attachments: HIVE-2146.1.patch, HIVE-2146.2.patch
>
>
> Now number of reducers of block sampling is not modified, so that queries like:
> select c from tab tablesample(1 percent) group by c;
> can generate huge number of reducers although the input is sampled to be small.
> We need to shrink number of reducers to make block sampling more useful.
> Since now number of reducers are determined before get splits, the way to do it probably is not clean enough, but we can do a good guess.

--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira