```
$ 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.
{
    if (buf.eof())
        return false;
    char c = *buf.position();
    if (!equalsCaseInsensitive(*s, c))
        return false;
    assertStringCaseInsensitive(s, buf);
    return true;
}
template <typename T>
static void appendToStringOrVector(T & s, ReadBuffer & rb, const char * end)
{
    s.append(rb.position(), end - rb.position());
}
template <>
inline void appendToStringOrVector(PaddedPODArray<UInt8> & s, ReadBuffer & rb, const char * end)
{
    if (rb.isPadded())
        s.insertSmallAllowReadWriteOverflow15(rb.position(), end);
    else
        s.insert(rb.position(), end);
}
template <>
inline void appendToStringOrVector(PODArray<char> & s, ReadBuffer & rb, const char * end)
{
    s.insert(rb.position(), end);
}
template <char... chars, typename Vector>
void readStringUntilCharsInto(Vector & s, ReadBuffer & buf)