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https://issues.apache.org/jira/browse/DRILL-3884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chun Chang closed DRILL-3884.
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Assignee: Chun Chang (was: Venki Korukanti)
verified fix.
> 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: Chun Chang
> 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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