| left_key, right_key, count, sort=sort | |
| ) | |
| if sort or len(left_ax) != len(left_indexer): | |
| # if asked to sort or there are 1-to-many matches | |
| join_index = left_ax.take(left_indexer) | |
| return join_index, left_indexer, right_indexer | |
| # left frame preserves order & length of its index | |
| return left_ax, None, right_indexer |