private long numValue(int colId) {
        if (rowDataAddr == 0) {
            throw new IllegalStateException("illegal row");
        }
        int offset = 0;
        if (creator.hasDims) {
            int realIndex = creator.colIdToIndex[colId];
            if (realIndex < creator.dimCount) {
                // A dim.
                offset = realIndex << 3;
            } else {
                // A metric.
                int metricIndex = realIndex - creator.dimCount;
                offset = dimDataSize + (metricIndex << 3);
            }
        } else {
            offset = colId << 3;
        }
        return MemoryUtil.getLong(rowDataAddr + offset);
    }
The aproximately memeory usage of this object. Currently only return the raw row data size.
indexr-segment/src/main/java/io/indexr/segment/rt/UTF8Row.java