{
RowMutation rm = new RowMutation(Keyspace.SYSTEM_KS, SystemKeyspace.getSchemaKSKey(ksName));
ColumnFamily cf = rm.addOrGet(SchemaColumnFamiliesCf);
int ldt = (int) (System.currentTimeMillis() / 1000);
ColumnNameBuilder builder = SchemaColumnFamiliesCf.getCfDef().getColumnNameBuilder();
builder.add(ByteBufferUtil.bytes(cfName));
cf.addAtom(new RangeTombstone(builder.build(), builder.buildAsEndOfRange(), timestamp, ldt));
for (ColumnDefinition cd : column_metadata.values())
cd.deleteFromSchema(rm, cfName, timestamp);
for (TriggerDefinition td : triggers.values())