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ASF GitHub Bot commented on HIVE-14160: --------------------------------------- GitHub user zhongdeyin opened a pull request: https://github.com/apache/hive/pull/85 [HIVE-14160]Optimized group by within distinct data skew proplem Jira issue: https://issues.apache.org/jira/browse/HIVE-14160 Modify GroupByOperator.endGroup() method, while keysCurrentGroup.size() is greater than a threshold(hive.distinct.setsize.max), will new a HashSet instead of clear set. Option hive.distinct.newset.max is the Maximum for getting new hashset, beyond this threshold,will still execute hashset.clear(). This will ensure task stability. User can set these two client parameters themselves. You can merge this pull request into a Git repository by running: $ git pull https://github.com/zhongdeyin/hive branch-1.1 Alternatively you can review and apply these changes as the patch at: https://github.com/apache/hive/pull/85.patch To close this pull request, make a commit to your master/trunk branch with (at least) the following in the commit message: This closes #85 ---- commit 390fb2e30d5043cd262ad73d3c1678a268c591e3 Author: zhongdeyin <zhong...@lenovo.com> Date: 2016-07-08T07:38:14Z Optimized group by within distinct data skew proplem ---- > Reduce-task costs a long time to finish on the condition that the certain sql > "select a,distinct(b) group by a" has been executed on the data which has > skew distribution > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- > > Key: HIVE-14160 > URL: https://issues.apache.org/jira/browse/HIVE-14160 > Project: Hive > Issue Type: Improvement > Components: hpl/sql > Affects Versions: 1.1.0 > Reporter: marymwu > > Reduce-task costs a long time to finish on the condition that the certain sql > "select a,distinct(b) group by a" has been executed on the data which has > skew distribution > data scale: 64G -- This message was sent by Atlassian JIRA (v6.3.4#6332)