hadoop-hdfs-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From 李洪忠 <lhz...@hotmail.com>
Subject Re: Mapper and Reducer takes longer than usual for a HBase table aggregation task
Date Mon, 26 Aug 2013 00:52:58 GMT
You need release your map code here to analyze the question. generally, 
when map/reduce hbase,  scanner with filter(s) is used. so the mapper 
count is the hbase region count in your hbase table.
As the reason why you reduce so slow, I guess, you have an disaster join 
on the three tables, which cause too many rows.

于 2013/8/26 4:36, Pavan Sudheendra 写道:
> Another Question, why does it indicate number of mappers as 1? Can i 
> change it so that multiple mappers perform computation?

View raw message