**Use case**

Workload generation with continuous queries.

**Describe the solution you'd like**

Similar to now() but non-constant.

{
public:
    static constexpr auto name = "now";
    String getName() const override { return name; }
    bool isDeterministic() const override { return false; }
    bool isVariadic() const override { return true; }
    size_t getNumberOfArguments() const override { return 0; }
    static FunctionOverloadResolverPtr create(ContextPtr) { return std::make_unique<NowOverloadResolver>(); }
    DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override
    {
        if (arguments.size() > 1)
        {
            throw Exception("Arguments size of function " + getName() + " should be 0 or 1", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
        }
        if (arguments.size() == 1 && !isStringOrFixedString(arguments[0].type))
        {
            throw Exception(
                "Arguments of function " + getName() + " should be String or FixedString", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
        }
        if (arguments.size() == 1)
        {
            return std::make_shared<DataTypeDateTime>(extractTimeZoneNameFromFunctionArguments(arguments, 0, 0));
        }
        return std::make_shared<DataTypeDateTime>();
    }
    FunctionBasePtr buildImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &) const override