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From "hyoungjunkim (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (TAJO-178) Implements StorageManager for scanning asynchronously
Date Thu, 12 Sep 2013 05:27:51 GMT

    [ https://issues.apache.org/jira/browse/TAJO-178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13765169#comment-13765169

hyoungjunkim commented on TAJO-178:

Issue name is changed cause misunderstood.
> Implements StorageManager for scanning asynchronously
> -----------------------------------------------------
>                 Key: TAJO-178
>                 URL: https://issues.apache.org/jira/browse/TAJO-178
>             Project: Tajo
>          Issue Type: Improvement
>          Components: storage
>    Affects Versions: 0.2-incubating
>            Reporter: hyoungjunkim
>            Assignee: hyoungjunkim
>         Attachments: TAJO-178_1.path, TAJO-178.patch_2, TAJO-178.path, tajo_storage_manager.png
> The current StorageManager does not provide scan scheduling function. All scan operations
run concurrently. This is the cause of random disk access and disk read performance is not
> The proposed StorageManager is based on double buffering. Each disk has a scheduler to
schedule by order of scanned adjust. Each Scanner has a InputStream and a Tuple pool. The
next() operation of ScanNode is blocked until Tuple pool is filled. Assigned Scanner by the
scheduler read data(xMB) and fills Tuple Pool and notifies to next() operation. After scanning
Scanner re-enter DiskScanQueue.
> In this way Scanner can pass column vector to Vectorized Query Engine.
> See the attached file.

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