Minor Description
We spotted a regression on nested queries in the Elastisearch nightly track:
https://elasticsearch-benchmarks.elastic.co/index.html#tracks/nested/nightly/30d
It seems related to the fact that we propagate the TOP_SCORES score mode to the child query even though we don't compute a max score in the BlockJoinScorer and don't propagate the minimum score either. Since it is not possible to compute a max score for a document that depends on other documents (the children) we should probably force the score mode to COMPLETE to build the child scorer. This should avoid the overhead of loading and reading the impacts. It should also be possible to early terminate queries that use the ScoreMode.None mode since in this case the score of each parent document is the same.