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https://issues.apache.org/jira/browse/HIVE-25448?focusedWorklogId=731641&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-731641
]
ASF GitHub Bot logged work on HIVE-25448:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 23/Feb/22 15:28
Start Date: 23/Feb/22 15:28
Worklog Time Spent: 10m
Work Description: dengzhhu653 edited a comment on pull request #2585:
URL: https://github.com/apache/hive/pull/2585#issuecomment-1048902780
I found something interesting, when I explain `select col1, count(distinct
col2) from partition_distinct_skew group by col1;` on master branch, the
output is following:
```
Vertices:
Map 1
Map Operator Tree:
TableScan
alias: partition_distinct_skew
Statistics: Num rows: 3 Data size: 510 Basic stats:
COMPLETE Column stats: COMPLETE
Select Operator
expressions: col1 (type: string), col2 (type: string)
outputColumnNames: col1, col2
Statistics: Num rows: 3 Data size: 510 Basic stats:
COMPLETE Column stats: COMPLETE
Group By Operator
keys: col1 (type: string), col2 (type: string)
minReductionHashAggr: 0.4
mode: hash
outputColumnNames: _col0, _col1
Statistics: Num rows: 2 Data size: 340 Basic stats:
COMPLETE Column stats: COMPLETE
Reduce Output Operator
key expressions: _col0 (type: string), _col1 (type:
string)
null sort order: zz
sort order: ++
Map-reduce partition columns: rand() (type: double)
Statistics: Num rows: 2 Data size: 340 Basic stats:
COMPLETE Column stats: COMPLETE
```
The partition column is **rand()** for this case. It's seems we have done
something to improve the skew case, though I'm not able to find where the cause
locates.
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Issue Time Tracking
-------------------
Worklog Id: (was: 731641)
Time Spent: 2h 40m (was: 2.5h)
> Invalid partition columns when skew with distinct
> -------------------------------------------------
>
> Key: HIVE-25448
> URL: https://issues.apache.org/jira/browse/HIVE-25448
> Project: Hive
> Issue Type: Bug
> Components: Logical Optimizer
> Reporter: Zhihua Deng
> Assignee: Zhihua Deng
> Priority: Major
> Labels: pull-request-available
> Time Spent: 2h 40m
> Remaining Estimate: 0h
>
> When hive.groupby.skewindata is enabled, we spray by the grouping key and
> distinct key if distinct is present in the first reduce sink operator.
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