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.
auto right_block = parent.getRightBlock(block_number);
            if (bitmaps.used(block_number))
            {
                IColumn::Filter not_used = bitmaps.getNotUsed(block_number);
                for (const auto & row : not_used)
                    if (row)
                        ++rows_added;
                for (size_t col = 0; col < columns_right.size(); ++col)
                {
                    
                    ColumnPtr portion = right_block->getByPosition(col).column->filter(not_used, 1);
                    columns_right[col]->insertRangeFrom(*portion, 0, portion->size());
                }
            }
            else
            {
                rows_added += right_block->rows();
                for (size_t col = 0; col < columns_right.size(); ++col)
                {
                    const IColumn & column = *right_block->getByPosition(col).column;
                    columns_right[col]->insertRangeFrom(column, 0, column.size());
                }
            }
            if (rows_added >= max_block_size)
                break;
        }
        return rows_added;
    }
};
BlockInputStreamPtr MergeJoin::createStreamWithNonJoinedRows(const Block & result_sample_block, UInt64 max_block_size) const