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From "Venki Korukanti (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-3884) Hive native scan has lower parallelization leading to performance degradation
Date Thu, 01 Oct 2015 23:26:26 GMT
Venki Korukanti created DRILL-3884:
--------------------------------------

             Summary: 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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