I was working on this project where I have deleted the column and I remember the definition of tombstone is that, you need to run compact so that the tombstone is removed. When I run nodetool compact, this message appear below.
INFO 19:15:09,170 Nothing to compact in index1. Use forceUserDefinedCompaction if you wish to force compaction of single sstables (e.g. for tombstone collection)
So what is this means is that, you need to have jconsole running because forceUserDefinedCompaction can only invoke through jconsole. When jconsole is connected to your cassandra daemon process, you need to navigate to the compactionmanager mbean.
Then you need to provide two value to this method as this method expected two parameters. That is the keyspace and the sstables where you wish to compact. You can see in this attachment on how I did it.
So if you ls the data directory where the sstable are store, a new sstable should be generated. Once the operation is complete, you can navigate to the data directory where the sstable is stored.
$ ls data/lucene1/
index1-hc-3-Data.db index1-hc-3-Digest.sha1 index1-hc-3-Filter.db index1-hc-3-Index.db index1-hc-3-Statistics.db snapshots
We have production machine which a single sstable size is more than 25GB. When the soft limit compaction is met (default min 4 and max 32) , in this situation, I think it will load the server if it takes place, probably best is, we forceUserDefinedCompaction on this single large sstable.