Details
Description
Currently DrillSideways implementation is based on the single threaded IndexSearcher.search(Query query, Collector results).
On large document set, the single threaded collection can be really slow.
The ParallelDrillSideways implementation could:
1. Use the CollectionManager based method IndexSearcher.search(Query query, CollectorManager collectorManager) to get the benefits of multithreading on index segments,
2. Compute each DrillSideway subquery on a single thread.