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Posted to dev@hive.apache.org by "Lefty Leverenz (JIRA)" <ji...@apache.org> on 2014/10/01 05:57:33 UTC
[jira] [Updated] (HIVE-7156) Group-By operator stat-annotation only
uses distinct approx to generate rollups
[ https://issues.apache.org/jira/browse/HIVE-7156?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Lefty Leverenz updated HIVE-7156:
---------------------------------
Labels: TODOC14 (was: )
> Group-By operator stat-annotation only uses distinct approx to generate rollups
> -------------------------------------------------------------------------------
>
> Key: HIVE-7156
> URL: https://issues.apache.org/jira/browse/HIVE-7156
> Project: Hive
> Issue Type: Sub-task
> Affects Versions: 0.14.0
> Reporter: Gopal V
> Assignee: Prasanth J
> Priority: Blocker
> Labels: TODOC14
> Fix For: 0.14.0
>
> Attachments: HIVE-7156.1.patch, HIVE-7156.2.patch, HIVE-7156.3.patch, HIVE-7156.4.patch, HIVE-7156.5.patch, HIVE-7156.6.patch, HIVE-7156.7.patch, HIVE-7156.8.patch, HIVE-7156.8.patch, HIVE-7156.9.patch, hive-debug.log.bz2
>
>
> The stats annotation for a group-by only annotates the reduce-side row-count with the distinct values.
> The map-side gets the row-count as the rows output instead of distinct * parallelism, while the reducer side gets the correct parallelism.
> {code}
> hive> explain select distinct L_SHIPDATE from lineitem;
> Vertices:
> Map 1
> Map Operator Tree:
> TableScan
> alias: lineitem
> Statistics: Num rows: 5999989709 Data size: 4745677733354 Basic stats: COMPLETE Column stats: COMPLETE
> Select Operator
> expressions: l_shipdate (type: string)
> outputColumnNames: l_shipdate
> Statistics: Num rows: 5999989709 Data size: 4745677733354 Basic stats: COMPLETE Column stats: COMPLETE
> Group By Operator
> keys: l_shipdate (type: string)
> mode: hash
> outputColumnNames: _col0
> Statistics: Num rows: 5999989709 Data size: 563999032646 Basic stats: COMPLETE Column stats: COMPLETE
> Reduce Output Operator
> key expressions: _col0 (type: string)
> sort order: +
> Map-reduce partition columns: _col0 (type: string)
> Statistics: Num rows: 5999989709 Data size: 563999032646 Basic stats: COMPLETE Column stats: COMPLETE
> Execution mode: vectorized
> Reducer 2
> Reduce Operator Tree:
> Group By Operator
> keys: KEY._col0 (type: string)
> mode: mergepartial
> outputColumnNames: _col0
> Statistics: Num rows: 1955 Data size: 183770 Basic stats: COMPLETE Column stats: COMPLETE
> Select Operator
> expressions: _col0 (type: string)
> outputColumnNames: _col0
> Statistics: Num rows: 1955 Data size: 183770 Basic stats: COMPLETE Column stats: COMPLETE
> {code}
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