private AbstractType<?> getTypeAndRemove(
        Map<ColumnIdentifier, AbstractType> columns, ColumnIdentifier t)
        throws InvalidRequestException {
      AbstractType type = columns.get(t);
      if (type == null)
        throw new InvalidRequestException(
            String.format("Unknown definition %s referenced in PRIMARY KEY", t));
      if (type instanceof CollectionType)
        throw new InvalidRequestException(
            String.format("Invalid collection type for PRIMARY KEY component %s", t));

      columns.remove(t);
      Boolean isReversed = definedOrdering.get(t);
      return isReversed != null && isReversed ? ReversedType.getInstance(type) : type;
    }
  public Collection<RowMutation> getMutations(
      List<ByteBuffer> variables, boolean local, ConsistencyLevel cl, long now)
      throws RequestExecutionException, RequestValidationException {
    // keys
    List<ByteBuffer> keys = UpdateStatement.buildKeyNames(cfDef, processedKeys, variables);

    // columns
    ColumnNameBuilder builder = cfDef.getColumnNameBuilder();
    CFDefinition.Name firstEmpty =
        UpdateStatement.buildColumnNames(cfDef, processedKeys, builder, variables, false);

    boolean fullKey = builder.componentCount() == cfDef.columns.size();
    boolean isRange = cfDef.isCompact ? !fullKey : (!fullKey || toRemove.isEmpty());

    if (!toRemove.isEmpty() && isRange)
      throw new InvalidRequestException(
          String.format(
              "Missing mandatory PRIMARY KEY part %s since %s specified",
              firstEmpty, toRemove.iterator().next().left));

    // Lists DISCARD operation incurs a read. Do that now.
    Set<ByteBuffer> toRead = null;
    for (Pair<CFDefinition.Name, Term> p : toRemove) {
      CFDefinition.Name name = p.left;
      Term value = p.right;

      if ((name.type instanceof ListType) && value != null) {
        if (toRead == null) toRead = new TreeSet<ByteBuffer>(UTF8Type.instance);
        toRead.add(name.name.key);
      }
    }

    Map<ByteBuffer, ColumnGroupMap> rows =
        toRead != null
            ? readRows(keys, builder, toRead, (CompositeType) cfDef.cfm.comparator, local, cl)
            : null;

    Collection<RowMutation> rowMutations = new ArrayList<RowMutation>(keys.size());
    UpdateParameters params = new UpdateParameters(variables, getTimestamp(now), -1);

    for (ByteBuffer key : keys)
      rowMutations.add(
          mutationForKey(
              cfDef, key, builder, isRange, params, rows == null ? null : rows.get(key)));

    return rowMutations;
  }