Mike McCandless writes:
In my last post I described a known limitation of BlockJoinQuery: it joins in only one direction (from child to parent documents). This can be a problem because some applications need to join in reverse (from parent to child documents) instead.
This is now fixed! I just committed a new query, ToChildBlockJoinQuery, to perform the join in the opposite direction. I also renamed the previous query to ToParentBlockJoinQuery.
This will included in Lucene 3.6.0 and 4.0.