Function decoded_cell_value 

pub fn decoded_cell_value(
    col: &DecodedColumn,
    row: usize,
    declared: &ColumnType,
) -> Result<Value, ColumnarError>

Row row of col as the Value the memtable reads for a cell of declared type.

A null cell or a row past the column is Value::Null. A cell whose bytes do not hold a value of declared type is a corrupt segment and an error.