Cassandra-Hector-Scala:How can I get all row Composite key in column family? - scala

Question

My data storage format is:
Family name :Test
Rowkey: comkey1:comkey2
=>(name=name,value='xyz',timestamp=1554515485)
-------------------------------------------------------
Rowkey: comkey1:comkey3
=>(name=name,value='abc',timestamp=1554515485)
-------------------------------------------------------
Rowkey: comkey1:comkey4
=>(name=name,value='pqr',timestamp=1554515485)
-------------------------------------------------------
now i want to fetch all composite key from "test" family
and i am trying
def test=Action{
val cluster = HFactory.getOrCreateCluster("Test Cluster", "127.0.0.1:9160");
val keyspace = HFactory.createKeyspace("winoriatest", cluster)
var startKey = new Composite();
var endKey= new Composite();
startKey.addComponent("comkey1", StringSerializer.get());
startKey.addComponent("comkey2", StringSerializer.get());
endKey.addComponent("comkey1", StringSerializer.get());
endKey.addComponent("comkey4", StringSerializer.get());
val rangeSlicesQuery = HFactory.createRangeSlicesQuery(keyspace, CompositeSerializer.get(), StringSerializer.get(),StringSerializer.get())
rangeSlicesQuery.setColumnFamily("test");
// CompositeSerializer.get() is not working.
rangeSlicesQuery.setKeys(startKey,endKey)
rangeSlicesQuery.setRange(null,null,false,Integer.MAX_VALUE);
rangeSlicesQuery.setReturnKeysOnly()
val result = rangeSlicesQuery.execute()
val orderedRows = result.get();
import scala.collection.JavaConversions._
for (sc <- orderedRows) {
println(sc.getKey())
}
Ok(views.html.index("Your new application is ready."))
}
Error :[NullPointerException: null] on line
val result = rangeSlicesQuery.execute()
Cassandra 2.0 scala 2.10.2
Thank you for your help in resolving this, in advance.
it giving me null pointer exception, and the same code is working with java
and my java code is
Cluster cluster = HFactory.getOrCreateCluster("Test Cluster","127.0.0.1:9160");
Keyspace keyspace = HFactory.createKeyspace("winoriatest", cluster);
Serializer<String> se= StringSerializer.get() ;
Serializer<Long> le= LongSerializer.get() ;
Serializer<Integer> ie= IntegerSerializer.get() ;
CompositeSerializer ce = new CompositeSerializer();
RangeSlicesQuery<Composite,String,byte[]> rangeSliceQuery=HFactory.createRangeSlicesQuery(keyspace,ce,se, BytesArraySerializer.get());
rangeSliceQuery.setColumnFamily("test");
rangeSliceQuery.setRange(null,null, false, Integer.MAX_VALUE);
QueryResult<OrderedRows<Composite,String,byte[]>>result=rangeSliceQuery.execute();
OrderedRows<Composite,String,byte[]> orderedRows=result.get();
for (Row<Composite,String,byte[]> r:orderedRows)
{
System.out.println("Compositekey="+r.getKey().get(0,se)+":"+r.getKey().get(1, se));
}

Answer 1

I'm not quite sure what "i want to fetch all composite key in test family" means. If you mean, you want to get just the partition [row] key components, then you can do this in CQL as simply as:
SELECT DISTINCT a, b FROM test
(Assigning a and b to be the column names.)
This is a good example of how much simpler CQL makes Cassandra development, which is why we're pushing people to use the native CQL driver over legacy clients like Hector.
For more on how CQL makes sense of a Thrift data model like this, see http://www.datastax.com/dev/blog/cql3-for-cassandra-experts.