**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.

{
        POINT,
        RANGE,
        UNKNOWN,
    };
    std::vector<Constraint> column_constraints(key_columns.size(), Constraint::UNKNOWN);
    for (const auto & element : rpn)
    {
        if (element.function == RPNElement::Function::FUNCTION_AND)
        {
            continue;
        }
        if (element.function == RPNElement::Function::FUNCTION_IN_SET && element.set_index && element.set_index->size() == 1)
        {
            column_constraints[element.key_column] = Constraint::POINT;
            continue;
        }
        if (element.function == RPNElement::Function::FUNCTION_IN_RANGE)
        {
            if (element.range.left == element.range.right)
            {
                column_constraints[element.key_column] = Constraint::POINT;
            }
            if (column_constraints[element.key_column] != Constraint::POINT)
            {