hadoop-hive-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HIVE-1118) Hive merge map files should have different bytes/mapper setting
Date Mon, 01 Feb 2010 22:04:30 GMT

     [ https://issues.apache.org/jira/browse/HIVE-1118?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zheng Shao updated HIVE-1118:
-----------------------------

    Assignee: Zheng Shao
      Status: Patch Available  (was: Open)

> Hive merge map files should have different bytes/mapper setting
> ---------------------------------------------------------------
>
>                 Key: HIVE-1118
>                 URL: https://issues.apache.org/jira/browse/HIVE-1118
>             Project: Hadoop Hive
>          Issue Type: Improvement
>            Reporter: Zheng Shao
>            Assignee: Zheng Shao
>         Attachments: HIVE-1118.1.patch
>
>
> Currently, by default, we get one reducer for each 1GB of input data.
> It's also true for the conditional merge job that will run if the average file size is
smaller than a threshold.
> This actually makes those job very slow, because each reducer needs to consume 1GB of
data.
> Alternatively, we can just use that threshold to determine the number of reducers per
job (or introduce a new parameter).
> Let's say the threshold is 1MB, then we only start the the merge job if the average file
size is less than 1MB, and the eventual result file size will be around 1MB (or another small
number).
> This will remove the extreme cases where we have thousands of empty files, but still
make normal jobs fast enough.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message