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From Aliou SOW <aliouji...@hotmail.com>
Subject INserting data in Cassandra
Date Wed, 11 Apr 2012 09:42:52 GMT



Hello
all,

We would like to
adopt Cassandra solution
for storing our biological data which
are essentially microarray data.

These data, formatted in text tabulated files, are in the form:



               Sample 1             sample
2             …            sample n

probe 1    value1                  value 2                 …            …





probe
2          

…

probe n



In fact the probes can vary from one chip to another
and you can have chips with more than one million probes,
the samples by cons
vary from one project to another,
the values ​​are floats.

So we would like to represent our column families like they are
formatted in files with the names of the probes (which are unique) as the key,
and the names of the samples as column names and float values as column values
:)

To insert data,
I just created such for example a keyspace testKS
and a column
family testCF but
just by defining the
key (because the column names
vary), then a
file jason for insertion:



{"probe1" :{

                "sample 1":value1(float),

                "sample 2":value2(float),

                …,

                "sample n":value n(float)

},

"probe2" :{

                "sample 1":value1(float),

                "sample 2":value2(float),

                …,

                "sample n":value n(float)

}

}



 

And I used the
tool json2sstable, but that does
not work, I
always have an error:



java.lang.RuntimeException:
Can't write Super columns to the Standard Column Family.



So I have two
questions:

1) What I did
wrong, must I define the complete structure of my column family before
using json2sstable or is it the structure of my json file which is not good?

2) Otherwise what would be the best way
to proceed for insertion based on the data I dispose?



We use Cassandra 1.0.8.
Any help would be welcome.



Thanks.

 		 	   		  
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