presto-main/src/main/java/io/prestosql/operator/scalar/MapHashCodeOperator.java/MapHashCodeOperator/hash
class MapHashCodeOperator:    @UsedByGeneratedCode
    public static long hash(MethodHandle keyHashCodeFunction, MethodHandle valueHashCodeFunction, Type keyType, Type valueType, Block block)
    {
        long result = 0;
        for (int position = 0; position < block.getPositionCount(); position += 2) {
            result += hashPosition(keyHashCodeFunction, keyType, block, position) ^ hashPosition(valueHashCodeFunction, valueType, block, position + 1);
        }
        return result;
    }