presto-hive/src/main/java/io/prestosql/plugin/hive/coercions/DecimalCoercers.java/DecimalCoercers/createDecimalToDoubleCoercer
class DecimalCoercers:    public static Function<Block, Block> createDecimalToDoubleCoercer(DecimalType fromType)
    {
        if (fromType.isShort()) {
            return new ShortDecimalToDoubleCoercer(fromType);
        }
        else {
            return new LongDecimalToDoubleCoercer(fromType);
        }
    }