presto-spi/src/main/java/io/prestosql/spi/type/LongDecimalType.java/LongDecimalType/hash
class LongDecimalType:    @Override
    public long hash(Block block, int position)
    {
        long low = block.getLong(position, 0);
        long high = block.getLong(position, SIZE_OF_LONG);
        return UnscaledDecimal128Arithmetic.hash(low, high);
    }