Querying CompositeType columns in Cassandra using Hector

Question

Here\'s a sample of the scenario I\'m facing. Say I have this column family:

    create column family CompositeTypeCF 
    with comparator = \'CompositeType(         


        

Answer 1

Good starting point tutorial here.

But, after finally having the need to use a composite component and attempting to write queries against the data, I figured out a few things that I wanted to share.

When searching Composite columns, the results will be a contiguous block of columns.

So, assuming a s composite of 3 Strings, and my columns look like:

A:A:A
A:B:B
A:B:C
A:C:B
B:A:A
B:B:A
B:B:B
C:A:B

For a search from A:A:A to B:B:B, the results will be

A:A:A
A:B:B
A:B:C
A:C:B
B:A:A
B:B:A
B:B:B

Notice the "C" Components? There are no "C" components in the start/end terms! what gives? These are all the results between A:A:A and B:B:B columns. The Composite search terms do not give the results as if processing nested loops (this is what I originally thought), but rather, since the columns are sorted, you are specifying the start and end terms for a contiguous block of columns.

When building the Composite search entries, you must specify the ComponentEquality

Only the last term should be GREATER_THAN_EQUAL, all the others should be EQUAL. e.g. for above

Composite start = new Composite();
start.addComponent(0, "A", Composite.ComponentEquality.EQUAL);
start.addComponent(1, "A", Composite.ComponentEquality.EQUAL);
start.addComponent(2, "A", Composite.ComponentEquality.EQUAL);

Composite end = new Composite();
end.addComponent(0, "B", Composite.ComponentEquality.EQUAL);
end.addComponent(1, "B", Composite.ComponentEquality.EQUAL);
end.addComponent(2, "B", Composite.ComponentEquality.GREATER_THAN_EQUAL);

SliceQuery<String, Composite, String> sliceQuery = HFactory.createSliceQuery(keyspace, se, ce, se);
sliceQuery.setColumnFamily("CF").setKey(myKey);
ColumnSliceIterator<String, Composite, String> csIterator = new ColumnSliceIterator<String, Composite, String>(sliceQuery, start, end, false);

while (csIterator.hasNext()) ....