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https://issues.apache.org/jira/browse/TAJO-385?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13849041#comment-13849041
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Hyunsik Choi commented on TAJO-385:
-----------------------------------
This is a just quick review. I'll review this patch in depth within few days.
Occasionally, this patch shows the number of completed tasks in SubQuery is
greater than the total number of tasks. Also, the query progress becomes higher
very fast in the early stage, and the progress becomes very slow as the query
proceeds. Probably, it is because the progress of an execution is _(c / n) *
100_, where _c_ is the number of completed tasks and _n_ is the total number of
tasks, and the total number of tasks is being increased during query processing.
> 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
>
>
> 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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