public void appendUTF8String(UTF8String val) {
            assert columnTypes[curColIndex] == SQLType.VARCHAR && val.numBytes() <= buffer.remaining();

            Platform.copyMemory(
                    val.getBaseObject(), val.getBaseOffset(),
                    buffer.array(), Platform.BYTE_ARRAY_OFFSET + buffer.arrayOffset() + buffer.position(), val.numBytes());
            buffer.position(buffer.position() + val.numBytes());
            curSums[curColIndex] = buffer.position();
            curColIndex++;
        }
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