Cassandra CQL3 Composite keys return duplicate values - cassandra

Question

I am new to CQL & composite keys (I previously used CLI)
I am looking to implement my old super-column-family with composite keys instead.
In short, my look-up model is:
blocks[file_id][position][block_id]=size
I have the folowing CQL table with composite keys:
CREATE TABLE blocks (
file_id text,
start_position bigint,
block_id text,
size bigint,
PRIMARY KEY (file_id, start_position,block_id)
);
I insert these sample values:
/*Example insertions*/
INSERT INTO blocks (file_id, start_position, block_id,size) VALUES ('test_schema_file', 0, 'testblock1', 500);
INSERT INTO blocks (file_id, start_position, block_id,size) VALUES ('test_schema_file', 500, '2testblock2', 501);
I query using this Astyanax code:
OperationResult result = m_keyspace.prepareQuery(m_BlocksTable).getKey(file).execute();
ColumnList<BlockKey> columns = (ColumnList<BlockKey>) result.getResult();
for (Column<BlockKey> column : columns) {
System.out.println(StaticUtils.fieldsToString(column.getName()));
try{
long value=column.getLongValue();
System.out.println(value);
}catch(Exception e){
System.out.println("Can't get size");
}
}
When I iterate over the result, I get 2 results for each column. One that contains a "size", and one where a "size" column doesn't exist.
recorder.data.models.BlockKey Object {
m_StartPosition: 0
m_BlockId: testblock1
m_Extra: null
}
Can't get size
recorder.data.models.BlockKey Object {
m_StartPosition: 0
m_BlockId: testblock1
m_Extra: size
}
500
recorder.data.models.BlockKey Object {
m_StartPosition: 500
m_BlockId: 2testblock2
m_Extra: null
}
Can't get size
recorder.data.models.BlockKey Object {
m_StartPosition: 500
m_BlockId: 2testblock2
m_Extra: size
}
501
So I have two questions:
Theoretically I do not need a size column, it should be a value of the composite key: blocks[file_id][position][block_id]=size instead of blocks[file_id][position][block_id]['size'] = size. . How do I correctly insert this data in CQL3 without creating the redundant size column?
Why am I getting the extra column without 'size', if I never inserted such a row?

Answer 1

The 'duplicates' are because, with CQL, there are extra thrift columns inserted to store extra metadata. With your example, from cassandra-cli you can see what's going on:
[default#ks1] list blocks;
------------------- RowKey: test_schema_file
=> (column=0:testblock1:, value=, timestamp=1373966136246000)
=> (column=0:testblock1:size, value=00000000000001f4, timestamp=1373966136246000)
=> (column=500:2testblock2:, value=, timestamp=1373966136756000)
=> (column=500:2testblock2:size, value=00000000000001f5, timestamp=1373966136756000)
If you insert data with CQL, you should query with CQL too. You can do this with Astyanax by using m_keyspace.prepareCqlStatement().withCql("SELECT * FROM blocks").execute();.