presto-hive/src/main/java/io/prestosql/plugin/hive/coercions/DecimalCoercers.java/DecimalCoercers/createDecimalToDecimalCoercer
class DecimalCoercers:    public static Function<Block, Block> createDecimalToDecimalCoercer(DecimalType fromType, DecimalType toType)
    {
        if (fromType.isShort()) {
            if (toType.isShort()) {
                return new ShortDecimalToShortDecimalCoercer(fromType, toType);
            }
            else {
                return new ShortDecimalToLongDecimalCoercer(fromType, toType);
            }
        }
        else {
            if (toType.isShort()) {
                return new LongDecimalToShortDecimalCoercer(fromType, toType);
            }
            else {
                return new LongDecimalToLongDecimalCoercer(fromType, toType);
            }
        }
    }