I have read through the following documentation: k-nearest neighbor (kNN) search | Elasticsearch Guide [master] | Elastic
I have also experimented with a small database and it seems that the results are skewed towards the matching function (which is BM25 (?)).
Matching score seems to be in a much higher magnitude as compared to KNN score. This can be further validated using the Explain API. Thus, is there any normalisation done to the matching values before adding to KNN score? Or we have to tune the values through boosting?