[jira] [Commented] (TAJO-385) Refactoring TaskScheduler to assign multiple fragments

["Jihoon Son (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TAJO-385?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13859953#comment-13859953 ] 

Jihoon Son commented on TAJO-385:
---------------------------------

I update the patch after rebasing and removing some duplicated codes caused by TAJO-468.
Review the patch, please.

> Refactoring TaskScheduler to assign multiple fragments
> ------------------------------------------------------
>
>                 Key: TAJO-385
>                 URL: https://issues.apache.org/jira/browse/TAJO-385
>             Project: Tajo
>          Issue Type: Improvement
>          Components: query master
>    Affects Versions: 0.8-incubating
>            Reporter: Jihoon Son
>            Assignee: Jihoon Son
>         Attachments: TAJO-385.patch, TAJO-385_2.patch, TAJO-385_3.patch, TAJO-385_4.patch, TAJO-385_5.patch
>
>
> In the current implementation, each task processes only one fragment.
> However, processing multiple fragments in a task will increase the query processing performance according to the storage layout and the user queries.
> In this issue, TaskScheduler is refactored to enable assigning multiple fragments to each task.
> Followings should be contained.
> * Schedule Fragments instead of QueryUnits in TaskScheduler
> ** The QueryUnit creation is postponed until TaskScheduler receives task requests from workers.
> ** When TaskScheduler receives task requests from workers, it dynamically creates an QueryUnit and assigns one or more fragments.
> ** The fragment scheduling should take into account the disk load balancing.



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