**Describe the situation**
https://markify.dev/p/zfrQMV2/text

**How to reproduce**
On aws `c5ad.24xlarge` run a query:

```
SET max_memory_usage = '100G', max_threads = 1000, max_insert_threads = 96

INSERT INTO wikistat WITH
    parseDateTimeBestEffort(extract(toLowCardinality(_path), 'pageviews-([\\d\\-]+)\\.gz$')) AS time,
    splitByChar(' ', line) AS values,
    splitByChar('.', values[1]) AS projects
SELECT
    time,
    projects[1] AS project,
    projects[2] AS subproject,
    values[2] AS path,
    CAST(values[3], 'UInt64') AS hits
FROM s3('https://....s3.eu-central-1.amazonaws.com/wikistat/original/*.gz', '...', '...', LineAsString, auto)
WHERE length(values) >= 3
```

Performance is not bad (22 million rows are inserted per second) but can be better.
char hex_code[4];
            if (4 != buf.read(hex_code, 4))
                return error("Cannot parse escape sequence: less than four bytes after \\u", ErrorCodes::CANNOT_PARSE_ESCAPE_SEQUENCE);
            
            if (0 == memcmp(hex_code, "0000", 4))
            {
                s.push_back(0);
                return ReturnType(true);
            }
            UInt16 code_point = unhex4(hex_code);
            if (code_point <= 0x7F)
            {
                s.push_back(code_point);
            }
            else if (code_point <= 0x07FF)
            {
                s.push_back(((code_point >> 6) & 0x1F) | 0xC0);
                s.push_back((code_point & 0x3F) | 0x80);
            }
            else
            {
                
                if (code_point >= 0xD800 && code_point <= 0xDBFF)
                {
                    if (!checkString("\\u", buf))
                        return error("Cannot parse escape sequence: missing second part of surrogate pair", ErrorCodes::CANNOT_PARSE_ESCAPE_SEQUENCE);
                    char second_hex_code[4];
                    if (4 != buf.read(second_hex_code, 4))
                        return error("Cannot parse escape sequence: less than four bytes after \\u of second part of surrogate pair",
                            ErrorCodes::CANNOT_PARSE_ESCAPE_SEQUENCE);