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From Hilmi Yildirim <hilmi.yildi...@neofonie.de>
Subject Re: Reading from HBase problem
Date Tue, 09 Jun 2015 08:34:54 GMT
Hi,
Now I tested the "count" method. It returns the same result as the 
flatmap.groupBy(0).sum(1) method.

Furthermore, the Hbase contains nearly 100 mio. rows but the result is 
102 mio.. This means that the HbaseInput reads more rows than the HBase 
contains.

Best Regards,
Hilmi

Am 08.06.2015 um 23:29 schrieb Fabian Hueske:
> Hi Hilmi,
>
> I see two possible reasons:
>
> 1) The data source / InputFormat is not properly working, so not all 
> HBase records are read/forwarded, or
> 2) The aggregation / count is buggy
>
> Roberts suggestion will use an alternative mechanism to do the count. 
> In fact, you can count with groupBy(0).sum() and accumulators at the 
> same time.
> If both counts are the same, this will indicate that the aggregation 
> is correct and hint that the HBase format is faulty.
>
> In any case, it would be very good to know your findings. Please keep 
> us updated.
>
> One more hint, if you want to do a full aggregate, you don't have to 
> use a "dummy" key like "a". Instead, you can work with Tuple1<Long> 
> and directly call sum(0) without doing the groupBy().
>
> Best, Fabian
>
> 2015-06-08 17:36 GMT+02:00 Robert Metzger <rmetzger@apache.org 
> <mailto:rmetzger@apache.org>>:
>
>     Hi Hilmi,
>
>     if you just want to count the number of elements, you can also use
>     accumulators, as described here [1].
>     They are much more lightweight.
>
>     So you need to make your flatMap function a RichFlatMapFunction,
>     then call getExecutionContext().
>     Use a long accumulator to count the elements.
>
>     If the results with the accumulator are consistent (the exact
>     element count), then there is a severe bug in Flink. But I suspect
>     that the accumulator will give you the same result (off by +-5)
>
>     Best,
>     Robert
>
>
>     [1]: http://slideshare.net/robertmetzger1/apache-flink-hands-on
>
>     On Mon, Jun 8, 2015 at 3:04 PM, Hilmi Yildirim
>     <hilmi.yildirim@neofonie.de <mailto:hilmi.yildirim@neofonie.de>>
>     wrote:
>
>         Hi,
>         I implemented a simple Flink Batch job which reads from an
>         HBase Cluster of 13 machines and with nearly 100 million rows.
>         The hbase version is 1.0.0-cdh5.4.1. So, I imported
>         hbase-client 1.0.0-cdh5.4.1.
>         I implemented a flatmap which creates a tuple ("a", 1L) for
>         each row . Then, I use groupBy(0).sum(1).writeAsTest. The
>         result should be the number of rows. But, the result is not
>         correct. I run the job multiple times and the result
>         flactuates by +-5. I also run the job for a smaller table with
>         100.000 rows and the result is correct.
>
>         Does anyone know the reason for that?
>
>         Best Regards,
>         Hilmi
>
>         -- 
>         --
>         Hilmi Yildirim
>         Software Developer R&D
>
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