```
$ 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.
{
    bool negative = false;
    make_unsigned_t<T> res = 0;
    auto on_error = []
    {
        if (throw_on_error)
            throwReadAfterEOF();
    };
    if (unlikely(buf.eof()))
        return on_error();
    if (is_signed_v<T> && *buf.position() == '-')
    {
        ++buf.position();
        negative = true;
        if (unlikely(buf.eof()))
            return on_error();
    }
    if (*buf.position() == '0') 
    {
        ++buf.position();
        x = 0;
        return;
    }
    while (!buf.eof())
    {
        unsigned char value = *buf.position() - '0';
        if (value < 10)
        {
            res *= 10;
            res += value;