You are viewing a plain text version of this content. The canonical link for it is here.
Posted to issues@drill.apache.org by "Venki Korukanti (JIRA)" <ji...@apache.org> on 2015/10/02 22:19:26 UTC
[jira] [Resolved] (DRILL-3884) Hive native scan has lower
parallelization leading to performance degradation
[ https://issues.apache.org/jira/browse/DRILL-3884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Venki Korukanti resolved DRILL-3884.
------------------------------------
Resolution: Fixed
> 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}}
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)