public SimpleRow buildAndReset() {
            Preconditions.checkState(curColIndex == curSums.length,
                    String.format("We have [%s] columns, by now inserted [%s]", curSums.length, curColIndex));

            int rowSize = curSums[curSums.length - 1];
            ByteBuffer data = ByteBuffer.allocate(rowSize);
            data.put(buffer.array(), 0, rowSize);
            SimpleRow r = new SimpleRow(data, curSums);

            buffer.clear();
            curSums = new int[columnTypes.length];
            curColIndex = 0;

            return r;
        }
A simple row can only store simple values like int, double, string. But cannot store multi-value column.
indexr-segment/src/main/java/io/indexr/segment/helper/SimpleRow.java