code: public void dropCf(UUID cfId)
      {
          assert columnFamilyStores.containsKey(cfId);
          ColumnFamilyStore cfs = columnFamilyStores.remove(cfId);
          if (cfs == null)
              return;
  
          // wait for any outstanding reads/writes that might affect the CFS
          cfs.keyspace.writeOrder.awaitNewBarrier();
          cfs.readOrdering.awaitNewBarrier();
  
          unloadCf(cfs);
      }
docs: best invoked on the compaction mananger.