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https://issues.apache.org/jira/browse/DRILL-3884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14940596#comment-14940596
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ASF GitHub Bot commented on DRILL-3884:
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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
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commit cdd71f1f2aa224f65147e084d75eacbc4ff7285b
Author: vkorukanti <[email protected]>
Date: 2015-10-01T22:15:12Z
DRILL-3884: Fix lower parallelization issues with Hive's native scan.
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> 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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