Why Secondary indexes is so slowly by my test?

[Chengying Fang]

Hi guys,


I found Secondary indexes too slowly in my product(amazon large instance) with 
cassandra, then I did test again as describe here. But the result is the same 
as product. What's wrong with cassandra or me?
Now my test:
newly installed ubuntu-12.04 LTS , apache-cassandra-1.1.6, default configure, 
just one keyspace(test) and one CF(TestIndex):

CREATE COLUMN FAMILY TestIndex  

    WITH comparator = UTF8Type  

    AND key_validation_class=UTF8Type  

    AND default_validation_class = UTF8Type  

    AND column_metadata = [  

        {column_name: tk, validation_class: UTF8Type, index_type: KEYS}  

        {column_name: from, validation_class: UTF8Type}  

        {column_name: to, validation_class: UTF8Type}  

        {column_name: tm, validation_class: UTF8Type}  

    ];

and 'tk' just three value:'A'(1000row),'B'(1000row),'X'(increment by test)
The test query from cql:
1,without index:select count(*) from TestIndex limit 1000000;
2,with index:select count(*) from TestIndex where tk='X' limit 1000000;
When I insert 60000 row 'X', the time:1s and 12s.
When 'X'  up to 130000,the time:2.3s and 33s.
When 'X'  up to 250000,the time:3.8s and 53s.


According to this, when 'X' up to billon, what's the result? Can Secondary 
indexes be used in product? I hope it's my mistake in doing this test.Can 
anyone give some tips about it?
Thanks in advance.
fancy