**Describe the bug**
Under certain conditions the equals comparison between String and Date yields the wrong result. Range Comparisons with greather-than-equals returns the correct result set.

**How to reproduce**
* Which ClickHouse server version to use: 21.2.5.5 (latest at the time of this issue)
* Which interface to use, if matters: HTTP (but should not matter)

```sql
CREATE TABLE default.myTable (
	myDay Date,
	myOrder Int32,
	someData String
) 
ENGINE = ReplacingMergeTree
PARTITION BY floor(toYYYYMMDD(myDay), -1)
ORDER BY (myOrder)
;

INSERT INTO default.myTable (myDay, myOrder) VALUES ('2021-01-01', 1);
INSERT INTO default.myTable (myDay, myOrder) VALUES ('2021-01-02', 2); // This row should be returned
INSERT INTO default.myTable (myDay, myOrder) VALUES ('2021-01-03', 3);

SELECT * FROM default.myTable mt
WHERE myDay = '2021-01-02';
```

**Expected behavior**
The last query in the example should yield the marked row. Instead it returns a empty result set.

There must be a connection to the used `PARTITION KEY`. The issue fails to reproduce as soon as I do any changes to the `PARTITION KEY` setting.

column_constraints[element.key_column] = Constraint::RANGE;
            }
            continue;
        }
        if (element.function == RPNElement::Function::FUNCTION_UNKNOWN)
        {
            continue;
        }
        return false;
    }
    auto min_constraint = column_constraints[0];
    if (min_constraint > Constraint::RANGE)
    {
        return false;
    }
    for (size_t i = 1; i < key_columns.size(); ++i)
    {
        if (column_constraints[i] < min_constraint)
        {
            return false;
        }
        if (column_constraints[i] == Constraint::RANGE && min_constraint == Constraint::RANGE)
        {
            return false;
        }
        min_constraint = column_constraints[i];
    }
    return true;
}
BoolMask KeyCondition::checkInHyperrectangle(