```
$ echo '20210101,A' | clickhouse-local --input-format CSV --structure 'd Date, s String' --query "SELECT * FROM table"
Code: 27. DB::Exception: Cannot parse input: expected ',' before: '20210101,A\n': 
Row 1:
Column 0,   name: d, type: Date,   ERROR: text "20210101,A" is not like Date

: While executing ParallelParsingBlockInputFormat: While executing File. (CANNOT_PARSE_INPUT_ASSERTION_FAILED)
```

**How to solve**

Disambiguate while parsing by absense of separators between YYYY-MM-DD.
{
    static constexpr bool throw_exception = std::is_same_v<ReturnType, void>;
    
    static constexpr auto date_time_broken_down_length = 19;
    
    static constexpr auto date_broken_down_length = 10;
    char s[date_time_broken_down_length];
    char * s_pos = s;
    /** Read characters, that could represent unix timestamp.
      * Only unix timestamp of at least 5 characters is supported.
      * Then look at 5th character. If it is a number - treat whole as unix timestamp.
      * If it is not a number - then parse datetime in YYYY-MM-DD hh:mm:ss or YYYY-MM-DD format.
      */