Class ToParentBlockJoinQuery

This query requires that you index children and parent docs as a single block, using the or API. In each block, the child documents must appear first, ending with the parent document. At search time you provide a identifying the parents, however this must provide an per sub-reader.

Once the block index is built, use this query to wrap any sub-query matching only child docs and join matches in that child document space up to the parent document space. You can then use this as a clause with other queries in the parent document space.

See ToChildBlockJoinQuery if you need to join in the reverse order.

The child documents must be orthogonal to the parent documents: the wrapped child query must never return a parent document.

If you'd like to retrieve ITopGroups<TGroupValue> for the resulting query, use the ToParentBlockJoinCollector. Note that this is not necessary, ie, if you simply want to collect the parent documents and don't need to see which child documents matched under that parent, then you can use any collector.

NOTE: If the overall query contains parent-only matches, for example you OR a parent-only query with a joined child-only query, then the resulting collected documents will be correct, however the ITopGroups<TGroupValue> you get from ToParentBlockJoinCollector will not contain every child for parents that had matched.

See http://lucene.apache.org/core/4_8_0/join/ for an overview.

@lucene.experimental