presto-rcfile/src/main/java/io/prestosql/rcfile/text/DecimalEncoding.java/DecimalEncoding/decodeColumn
class DecimalEncoding:    @Override
    public Block decodeColumn(ColumnData columnData)
    {
        int size = columnData.rowCount();
        BlockBuilder builder = type.createBlockBuilder(null, size);

        Slice slice = columnData.getSlice();
        for (int i = 0; i < size; i++) {
            int offset = columnData.getOffset(i);
            int length = columnData.getLength(i);
            if (length == 0 || nullSequence.equals(0, nullSequence.length(), slice, offset, length)) {
                builder.appendNull();
            }
            else if (isShortDecimal(type)) {
                type.writeLong(builder, parseLong(slice, offset, length));
            }
            else {
                type.writeSlice(builder, parseSlice(slice, offset, length));
            }
        }
        return builder.build();
    }