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 │   │
└────────────┴───┴───┘
```

{
    size_t res = 0;
    for (const auto & element : rpn)
    {
        if (element.function == RPNElement::FUNCTION_NOT_IN_RANGE
            || element.function == RPNElement::FUNCTION_IN_RANGE
            || element.function == RPNElement::FUNCTION_IN_SET
            || element.function == RPNElement::FUNCTION_NOT_IN_SET)
        {
            if (element.key_column > res)
                res = element.key_column;
        }
    }
    return res;
}
bool KeyCondition::hasMonotonicFunctionsChain() const
{
    for (const auto & element : rpn)
        if (!element.monotonic_functions_chain.empty()
            || (element.set_index && element.set_index->hasMonotonicFunctionsChain()))
            return true;
    return false;
}
}