Venki Korukanti created DRILL-3884:
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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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