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HBase, mail # user - Wrong HBase Sort Order with Pig


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Re: Wrong HBase Sort Order with Pig
John 2013-09-13, 17:11
Hi, thanks for your answer. I solved the problem. Here is the answer from
another mailing list:

The problem is that HBaseStorage maps
columns families into a HashMap, so the sort ordering is completely lost.

You have two options:

1. Modify HBaseStorage to use a SortedMap data structure (i.e. TreeMap) and
use the modified HBaseStorage. (or make it configurable)
2. Since you convert the map to a bag, you can sort the bag in a nested
foreach statement.

I prefer option 1 myself because it would be more performant than option 2.

Thanks anyway!
2013/9/13 Paulo Ricardo Paz Vital <[EMAIL PROTECTED]>

> Hello John,
>
> Are you running HBase and Pig with IBM Java?
>
> We found an error in one Pig unit test when building with IBM Java and
> looks like the problem is the same you are reporting. Please, check the
> JIRA [1] that's explaining the problem in Pig and the solution there.
>
> [1] https://issues.apache.org/jira/browse/PIG-3309
>
> If the error is the same and you are using IBM Java, the problem is how
> HashMap implementation of IBM order the map - it's different from
> Oracle's (Sun) implementation.
>
> Best regards,
> Paulo Vital
>
> On Fri, 2013-09-13 at 16:38 +0200, John wrote:
> > Hi, I already ask this on the pig mailing list. But because I'm not sure
> if
> > it is a Pig or HBase issue, I will ask here too since the Pig Function is
> > using a hbae scan operation. Here is my Questions:
> >
> > I have created a HBase Table in the hbase shell and added some data. In
> > http://hbase.apache.org/book/dm.sort.html is written that the datasets
> are
> > first sorted by the rowkey and then the column. So I tried something in
> the
> > HBase Shell: http://pastebin.com/gLVAX0rJ
> >
> > Everything looks fine. I got the right order a -> c -> d like expected.
> >
> > Now I tried the same with Apache Pig in Java:
> http://pastebin.com/jdTpj4Fu
> >
> > I got this result:
> >
> > (key1,[c#val,d#val,a#val])
> >
> > So, now the order is c -> d -> a. That seems a little odd to me,
> shouldn't
> > it be the same like in HBase? It's important for me to get the right
> order
> > because I transform the map afterwards into a bag and then join it with
> > other tables. If both inputs are sorted I could use a merge join without
> > sorting these two datasets. So does anyone know how it is possible to get
> > the sorted map (or bag) of the columns?
> >
> >
> > thanks
>
> --
> Paulo Ricardo Paz Vital <[EMAIL PROTECTED]>
> IBM Linux Technology Center
>
>