CFMetaData oldCfm = Schema.instance.getCFMetaData(ksName, cfName);
if (oldCfm == null)
throw new ConfigurationException(String.format("Cannot drop non existing column family '%s' in keyspace '%s'.", cfName, ksName));
logger.info(String.format("Drop ColumnFamily '%s/%s'", oldCfm.ksName, oldCfm.cfName));
announce(oldCfm.dropFromSchema(FBUtilities.timestampMicros()));
}
/**
* actively announce a new version to active hosts via rpc
* @param schema The schema mutation to be applied