[jira] [Commented] (DRILL-3884) Hive native scan has lower parallelization leading to performance degradation

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-3884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14940596#comment-14940596 ] 

ASF GitHub Bot commented on DRILL-3884:
---------------------------------------

GitHub user vkorukanti opened a pull request:

    https://github.com/apache/drill/pull/185

    DRILL-3884: Fix lower parallelization issues with Hive's native scan.

    @amansinha100 Could you please review the patch?

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/vkorukanti/drill DRILL-3884

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/drill/pull/185.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #185
    
----
commit cdd71f1f2aa224f65147e084d75eacbc4ff7285b
Author: vkorukanti <ve...@gmail.com>
Date:   2015-10-01T22:15:12Z

    DRILL-3884: Fix lower parallelization issues with Hive's native scan.

----


> Hive native scan has lower parallelization leading to performance degradation
> -----------------------------------------------------------------------------
>
>                 Key: DRILL-3884
>                 URL: https://issues.apache.org/jira/browse/DRILL-3884
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Query Planning & Optimization, Storage - Hive
>    Affects Versions: 1.2.0
>            Reporter: Venki Korukanti
>            Assignee: Venki Korukanti
>            Priority: Critical
>             Fix For: 1.2.0
>
>
> Currently {{HiveDrillNativeParquetScan.getScanStats()}} divides the rowCount got from {{HiveScan}} by a factor and returns that as cost. Problem is all cost calculations and parallelization depends on the rowCount. Value {{cpuCost}} is not taken into consideration in current cost calculations in {{ScanPrel}}. In order for the planner to choose {{HiveDrillNativeParquetScan}} over {{HiveScan}}, rowCount has to be lowered for the former, but this leads to lower parallelization and performance degradation.
> Temporary fix for Drill 1.2 before DRILL-3856 fully resolves considering CPU cost in cost model:
> 1. Change ScanPrel to consider the CPU cost in given Stats from GroupScan
> 2. Have higher CPU cost for {{HiveScan}} (SerDe route)
> 3. Lower CPU cost for {{HiveDrillNativeParquetScan}}



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