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Re: Some Hbase questions
For #b, take a look
at src/main/java/org/apache/hadoop/hbase/client/coprocessor/AggregationClient.java
in 0.94
It supports avg, max, min and sum operations through calling coprocessors.
Here is snippet from its javadoc:

 * This client class is for invoking the aggregate functions deployed on the
 * Region Server side via the AggregateProtocol. This class will implement
 * supporting functionality for summing/processing the individual results
 * obtained from the AggregateProtocol for each region.

For #c, running HBase and MR on the same cluster is acceptable. If you have
additional hardware, you can run mapreduce jobs on separate machines where
region server is not running.


On Sun, May 19, 2013 at 8:29 AM, Vivek Padmanabhan

> Hi,
>   I am pretty new to HBase so it would be great if someone could help me
> out with my below queries;
> (Ours is a time series data and all the queries will be range scan on
>  composite row keys)
> a) What is the usual practice of storing data types.
>    We have noticed that converting datatypes to bytes render unreadable
> data while debugging.
>    For ids, or int values we see the byte representation. So for some
> important columns
>    we converted into  datatype -> characters ->bytes, rather than datatype
> -> bytes
>    (May be we can write a wrapper over hbase shell to solve this. But is
> there a simpler way)
> b) What is the best way to achieve operations like AVG,SUM or some custom
> formula for real time queries. Coprocessors or in-memory with query result?
>    (The formula that we apply might get changed at any time so storing
> result is not an option)
> c) We are planning to start off with a four node cluster, having both
> HBase and MR jobs running.
>    I have heard that it is not recommended to have both HBase and MR on
> the same cluster, but I would
>    like to understand what could be the possible bottle necks.
>   (We plan to run MR on HDFS and MR on Hbase. Most of our MR jobs are IO
> bound rather than CPU bound)
> Thanks
> Vivek