public void appendLong(long val) {
            assert columnTypes[curColIndex] == SQLType.BIGINT
                    || columnTypes[curColIndex] == SQLType.DATE
                    || columnTypes[curColIndex] == SQLType.DATETIME;

            buffer.putLong(val);
            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