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No of Reducers are not working on Hive


No of Reducers are not working on Hive


I have set the No of reducers to 2 but still Hive is executing with 1.Any body help on this

set hive.exec.reducers.max=2

Hive (default)> insert overwrite directory '/input123456'
              > select count(*) from partitioned_user;
Total jobs = 1
Launching Job 1 out of 1
Number of reduce tasks determined at compile time: 1
In order to change the average load for a reducer (in bytes):
  set hive.exec.reducers.bytes.per.reducer=<number>
In order to limit the maximum number of reducers:
  set hive.exec.reducers.max=<number>
In order to set a constant number of reducers:
  set mapred.reduce.tasks=<number>
Starting Job = job_201810122125_0003, Tracking URL = http://ubuntu:50030/jobdetails.jsp?jobid=job_201810122125_0003
Kill Command = /home/naresh/Work1/hadoop-1.2.1/libexec/../bin/hadoop job  -kill job_201810122125_0003
Hadoop job information for Stage-1: number of mappers: 1; number of reducers: 1
2018-10-12 21:36:24,774 Stage-1 map = 0%,  reduce = 0%
2018-10-12 21:36:32,825 Stage-1 map = 100%,  reduce = 0%, Cumulative CPU 4.12 sec
2018-10-12 21:36:41,919 Stage-1 map = 100%,  reduce = 33%, Cumulative CPU 4.12 sec
2018-10-12 21:36:42,926 Stage-1 map = 100%,  reduce = 100%, Cumulative CPU 6.38 sec
MapReduce Total cumulative CPU time: 6 seconds 380 msec
Ended Job = job_201810122125_0003
Moving data to: /input123456
MapReduce Jobs Launched: 
Job 0: Map: 1  Reduce: 1   Cumulative CPU: 6.38 sec   HDFS Read: 354134 HDFS Write: 5 SUCCESS
Total MapReduce CPU Time Spent: 6 seconds 380 msec
Time taken: 37.199 seconds


Re: No of Reducers are not working on Hive

Expert Contributor

In count(*) query, final aggregation vertex should always be single task which fetches count of all the mappers & sumup all of the them.

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