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https://issues.apache.org/jira/browse/HIVE-219?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12662408#action_12662408
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David Phillips commented on HIVE-219:
-------------------------------------
With map-side:
{noformat}
hive> set hive.map.aggr=true;
hive> select count(1) from search_result;
Total MapReduce jobs = 1
Number of reducers = 7
...
OK
4012275
4011646
4011059
4008870
4011555
4014719
4013710
Time taken: 169.683 seconds
{noformat}
Without:
{noformat}
hive> set hive.map.aggr=false;
hive> select count(1) from search_result;
Total MapReduce jobs = 2
Number of reducers = 7
...
OK
28083834
Time taken: 204.804 seconds
{noformat}
> Map-side aggregates output one row per reducer when not grouping
> ----------------------------------------------------------------
>
> Key: HIVE-219
> URL: https://issues.apache.org/jira/browse/HIVE-219
> Project: Hadoop Hive
> Issue Type: Bug
> Components: Query Processor
> Reporter: David Phillips
> Priority: Critical
>
> Example: SELECT count(1) FROM table;
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