**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.
if (checkCharCaseInsensitive('u', buf))
        {
            assertStringCaseInsensitive("ll", buf);
            s.append("NULL");
        }
        else
        {
            assertStringCaseInsensitive("an", buf);
            s.append("NaN");
        }
    }
    else
    {
        
        auto parse_func = [](ReadBuffer & in)
        {
            Float64 tmp;
            readFloatText(tmp, in);
        };
        readParsedValueIntoString(s, buf, parse_func);
    }
}
void readJSONFieldIntoString(String & s, ReadBuffer & buf)
{
    auto parse_func = [](ReadBuffer & in) { skipJSONField(in, "json_field"); };
    readParsedValueIntoString(s, buf, parse_func);
}
}