Thankfully "partial merge join" is disabled by default.

```
milovidov-desktop :) SET max_block_size = 6, join_algorithm = 'partial_merge'

SET max_block_size = 6, join_algorithm = 'partial_merge'

Query id: 600704b7-b455-4726-8a9c-8e45b509f2fb

Ok.

0 rows in set. Elapsed: 0.002 sec. 

milovidov-desktop :) SELECT blockSize() bs FROM (SELECT 1 s) js1 ALL RIGHT JOIN (SELECT arrayJoin([2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3]) s) js2 USING (s) GROUP BY bs ORDER BY bs;

SELECT blockSize() AS bs
FROM
(
    SELECT 1 AS s
) AS js1
ALL RIGHT JOIN
(
    SELECT arrayJoin([2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3]) AS s
) AS js2 USING (s)
GROUP BY bs
ORDER BY bs ASC

Query id: ae51c589-4b69-4e90-a3a9-7ef4ead72af9

→ Progress: 2.00 rows, 2.00 B (18.21 rows/s., 18.21 B/s.)
```

Found by stress test.
{
    ExtraBlockPtr tmp;
    join->joinBlock(header, tmp);
    return header;
}
JoiningTransform::JoiningTransform(
    Block input_header,
    JoinPtr join_,
    size_t max_block_size_,
    bool on_totals_,
    bool default_totals_,
    FinishCounterPtr finish_counter_)
    : IProcessor({input_header}, {transformHeader(input_header, join_)})
    , join(std::move(join_))
    , on_totals(on_totals_)
    , default_totals(default_totals_)
    , finish_counter(std::move(finish_counter_))
    , max_block_size(max_block_size_)
{
    if (!join->isFilled())
        inputs.emplace_back(Block(), this);
}
IProcessor::Status JoiningTransform::prepare()