In this blog we introduce hybrid retrieval and explore two concrete implementations in Elasticsearch. We explore improving Elastic Learned Sparse EncodeR’s performance by combining it with BM25 using Reciprocal Rank Fusion and Weighted Sum of Scores.

In this blog post, we'll examine benchmark solutions to compare retrieval methods. We use a collection of data sets to benchmark BM25 against two dense models and illustrate the potential gain using fine-tuning strategies with one of those models.

In this first blog post, we will list and explain the differences between the primary building blocks available in the Elastic Stack to do information retrieval.