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https://issues.apache.org/jira/browse/HIVE-24471?focusedWorklogId=522547&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-522547
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ASF GitHub Bot logged work on HIVE-24471:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 10/Dec/20 04:51
Start Date: 10/Dec/20 04:51
Worklog Time Spent: 10m
Work Description: maheshk114 commented on a change in pull request #1736:
URL: https://github.com/apache/hive/pull/1736#discussion_r539843531
##########
File path: ql/src/java/org/apache/hadoop/hive/ql/exec/GroupByOperator.java
##########
@@ -712,6 +751,12 @@ private void processKey(Object row,
@Override
public void process(Object row, int tag) throws HiveException {
+ if (hashAggr) {
+ if (getConfiguration().get("forced.streaming.mode",
"false").equals("true")) {
Review comment:
i have removed it in the next commit ..had added for test only.
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Issue Time Tracking
-------------------
Worklog Id: (was: 522547)
Time Spent: 1h 20m (was: 1h 10m)
> Add support for combiner in hash mode group aggregation
> --------------------------------------------------------
>
> Key: HIVE-24471
> URL: https://issues.apache.org/jira/browse/HIVE-24471
> Project: Hive
> Issue Type: Bug
> Components: Hive
> Reporter: mahesh kumar behera
> Assignee: mahesh kumar behera
> Priority: Major
> Labels: pull-request-available
> Time Spent: 1h 20m
> Remaining Estimate: 0h
>
> In map side group aggregation, partial grouped aggregation is calculated to
> reduce the data written to disk by map task. In case of hash aggregation,
> where the input data is not sorted, hash table is used. If the hash table
> size increases beyond configurable limit, data is flushed to disk and new
> hash table is generated. If the reduction by hash table is less than min hash
> aggregation reduction calculated during compile time, the map side
> aggregation is converted to streaming mode. So if the first few batch of
> records does not result into significant reduction, then the mode is switched
> to streaming mode. This may have impact on performance, if the subsequent
> batch of records have less number of distinct values. To mitigate this
> situation, a combiner can be added to the map task after the keys are sorted.
> This will make sure that the aggregation is done if possible and reduce the
> data written to disk.
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