21.5.1
```sql

create table test(d Date, k Int64, s String) 
Engine=MergeTree partition by (toYYYYMM(d),k) order by (d, k)

insert into test values ('2020-01-01', 1, '');
insert into test values ('2020-01-02', 1, '');

SELECT * FROM test WHERE d != '2020-01-01'
0 rows in set. Elapsed: 0.003 sec.


SELECT * FROM test WHERE identity(d) !=  '2020-01-01';
┌──────────d─┬─k─┬─s─┐
│ 2020-01-02 │ 1 │   │
└────────────┴───┴───┘

SELECT * FROM test WHERE toDate(d) != '2020-01-01';
┌──────────d─┬─k─┬─s─┐
│ 2020-01-02 │ 1 │   │
└────────────┴───┴───┘
```

{
    /** Functions < > = != <= >= in `notIn`, where one argument is a constant, and the other is one of columns of key,
      *  or itself, wrapped in a chain of possibly-monotonic functions,
      *  or constant expression - number.
      */
    Field const_value;
    DataTypePtr const_type;
    if (const auto * func = node->as<ASTFunction>())
    {
        const ASTs & args = func->arguments->children;
        DataTypePtr key_expr_type;    
        size_t key_column_num = -1;   
        MonotonicFunctionsChain chain;
        std::string func_name = func->name;
        if (atom_map.find(func_name) == std::end(atom_map))
            return false;
        if (args.size() == 1)
        {
            if (!(isKeyPossiblyWrappedByMonotonicFunctions(args[0], context, key_column_num, key_expr_type, chain)))
                return false;
            if (key_column_num == static_cast<size_t>(-1))
                throw Exception("`key_column_num` wasn't initialized. It is a bug.", ErrorCodes::LOGICAL_ERROR);
        }
        else if (args.size() == 2)
        {
            size_t key_arg_pos;           
            bool is_set_const = false;
            bool is_constant_transformed = false;