This is the closest I can find in Jira https://issues.apache.org/jira/browse/CASSANDRA-4478
It's a pretty handy tool to have in your tool kit, specially when you start to have over 1 billion rows per node.
Freelance Cassandra Consultant
I heard a rumor that index_interval is going away? What is the replacement for this? (we have been having to play with this setting a lot lately as too big and it gets slow yet too small and cassandra uses way too much RAM…we are still trying to find the right balance with this setting).