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https://issues.apache.org/jira/browse/HIVE-24207?focusedWorklogId=495812&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-495812
]
ASF GitHub Bot logged work on HIVE-24207:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 06/Oct/20 09:50
Start Date: 06/Oct/20 09:50
Worklog Time Spent: 10m
Work Description: abstractdog opened a new pull request #1556:
URL: https://github.com/apache/hive/pull/1556
Change-Id: I12d2719acdf80ffa3a5c14b1c3fce2d4cbe00911
### What changes were proposed in this pull request?
Using an object cache, LimitOperator/VectorLimitOperator/TezProcessor can
exit quickly if a limit is already reached.
### Why are the changes needed?
Performance benefit.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Tested on cluster.
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Issue Time Tracking
-------------------
Worklog Id: (was: 495812)
Remaining Estimate: 0h
Time Spent: 10m
> LimitOperator can leverage ObjectCache to bail out quickly
> ----------------------------------------------------------
>
> Key: HIVE-24207
> URL: https://issues.apache.org/jira/browse/HIVE-24207
> Project: Hive
> Issue Type: Improvement
> Reporter: Rajesh Balamohan
> Assignee: László Bodor
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> {noformat}
> select ss_sold_date_sk from store_sales, date_dim where date_dim.d_year in
> (1998,1998+1,1998+2) and store_sales.ss_sold_date_sk = date_dim.d_date_sk
> limit 100;
> select distinct ss_sold_date_sk from store_sales, date_dim where
> date_dim.d_year in (1998,1998+1,1998+2) and store_sales.ss_sold_date_sk =
> date_dim.d_date_sk limit 100;
> {noformat}
> Queries like the above generate a large number of map tasks. Currently they
> don't bail out after generating enough amount of data.
> It would be good to make use of ObjectCache & retain the number of records
> generated. LimitOperator/VectorLimitOperator can bail out for the later tasks
> in the operator's init phase itself.
> https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorLimitOperator.java#L57
> https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/exec/LimitOperator.java#L58
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