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 │   │
└────────────┴───┴───┘
```

{
public:
    enum Kind
    {
        NO_CONST = 0,
        LEFT_CONST,
        RIGHT_CONST,
    };
    explicit FunctionWithOptionalConstArg(const FunctionBasePtr & func_) : func(func_) {}
    FunctionWithOptionalConstArg(const FunctionBasePtr & func_, const ColumnWithTypeAndName & const_arg_, Kind kind_)
        : func(func_), const_arg(const_arg_), kind(kind_)
    {
    }
    String getName() const override { return func->getName(); }
    const DataTypes & getArgumentTypes() const override { return func->getArgumentTypes(); }
    const DataTypePtr & getResultType() const override { return func->getResultType(); }
    ExecutableFunctionPtr prepare(const ColumnsWithTypeAndName & arguments) const override { return func->prepare(arguments); }