```
$ 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>;
    auto error = []
    {
        if constexpr (throw_exception)
            throw Exception("Cannot parse date: value is too short", ErrorCodes::CANNOT_PARSE_DATE);
        return ReturnType(false);
    };
    auto ignore_delimiter = [&]
    {
        if (!buf.eof() && !isNumericASCII(*buf.position()))
        {
            ++buf.position();
            return true;
        }
        else
            return false;
    };
    auto append_digit = [&](auto & x)
    {
        if (!buf.eof() && isNumericASCII(*buf.position()))
        {
            x = x * 10 + (*buf.position() - '0');
            ++buf.position();