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From Silvère Lestang <silvere.lest...@gmail.com>
Subject Issues with MapReduce Job (using Brisk)
Date Tue, 31 May 2011 11:00:47 GMT
Hi,
I try to create a MapReduce job that calculate the average of values stored
in cassandra and write the result back to cassandra (using
ColumnFamilyOutputFormat and ColumnFamilyInputFormat). I use the Brisk
distribution of Hadoop but I don't know if it's somehow related.
My code is here: http://pastebin.com/8gd21VuP
As I understand in the WordCount example, the first parameters of the map
method is the row key and the second one is a map of <column.name, column>.
I found confirmation of this in the class ColumnFamilyRecordReader.
But my code didn't works. I dumped the row key and the column name using
logger and I saw that both seems to be get_range_slices objects, which is
very unexpected.
Here is an example of log (the CF contains 5 rows called row[0-4] with 10
columns each called columnKey[0-9] with value 42 ( * in ascii)):

*MAP rowkey*:
get_range_slicesrow1columnKey0*`columnKey1*acolumnKey2*bcolumnKey3*ccolumnKey4*dcolumnKey5*ecolumnKey6*fcolumnKey7*gcolumnKey8*hcolumnKey9*Hrow2columnKey0*columnKey1*columnKey2*columnKey3*columnKey4*columnKey5*columnKey6*columnKey7*columnKey8*columnKey9*row4columnKey0*pcolumnKey1*qcolumnKey2*rcolumnKey3*XcolumnKey4*YcolumnKey5*ZcolumnKey6*[columnKey7*@columnKey8*AcolumnKey9*Brow3columnKey0*columnKey1*columnKey2*columnKey3*columnKey4*columnKey5*columnKey6*columnKey7*columnKey8*columnKey9*row0columnKey0*columnKey1*:columnKey2*:!columnKey3*:"columnKey4*:#columnKey5*>columnKey6*>columnKey7*>columnKey8*>columnKey9*>

*MAP columnKey:*get_range_slicesrow1columnKey0*`columnKey1*acolumnKey2*bcolumnKey3*ccolumnKey4*dcolumnKey5*ecolumnKey6*fcolumnKey7*gcolumnKey8*hcolumnKey9*Hrow2columnKey0*columnKey1*columnKey2*columnKey3*columnKey4*columnKey5*columnKey6*columnKey7*columnKey8*columnKey9*row4columnKey0*pcolumnKey1*qcolumnKey2*rcolumnKey3*XcolumnKey4*YcolumnKey5*ZcolumnKey6*[columnKey7*@columnKey8*AcolumnKey9*Brow3columnKey0*columnKey1*columnKey2*columnKey3*columnKey4*columnKey5*columnKey6*columnKey7*columnKey8*columnKey9*row0columnKey0*columnKey1*:columnKey2*:!columnKey3*:"columnKey4*:#columnKey5*>columnKey6*>columnKey7*>columnKey8*>columnKey9*>


I can't understand why I get this instead of row key and column key, if
anybody have an idea?
Silvère

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