What is DFS in Elasticsearch "DFS_QUERY_THEN_FETCH"?

Question

What is DFS in Elasticsearch "DFS_QUERY_THEN_FETCH"?

what is the abbreviations of DFS?

Answer 1

The DFS stands for "Distributed Frequency Search".
Excerpt from the elasticsearch documentation :

The second workaround is to add ?search_type=dfs_query_then_fetch to your search requests. The dfs stands for Distributed Frequency Search, and it tells Elasticsearch to first retrieve the local IDF from each shard in order to calculate the global IDF across the whole index.

Tip Don’t use dfs_query_then_fetch in production. It really isn’t required. Just having enough data will ensure that your term frequencies are well distributed. There is no reason to add this extra DFS step to every query that you r