code: public void deleteFromSchema(Mutation mutation, long timestamp)
      {
          ColumnFamily cf = mutation.addOrGet(CFMetaData.SchemaColumnsCf);
          int ldt = (int) (System.currentTimeMillis() / 1000);
  
          // Note: we do want to use name.toString(), not name.bytes directly for backward compatibility (For CQL3, this won't make a difference).
          Composite prefix = CFMetaData.SchemaColumnsCf.comparator.make(cfName, name.toString());
          cf.addAtom(new RangeTombstone(prefix, prefix.end(), timestamp, ldt));
      }
docs: Drop specified column from the schema using given mutation.
  
  @param mutation  The schema mutation
  @param timestamp The timestamp to use for column modification