**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 (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)