Difference between Elasticsearch Range Query and Range Filter

Question

I want to query elasticsearch documents within a date range. I have two options now, both work fine for me. Have tested both of them. 1. Range Query 2. Range Filter

Since I have a small data set for now, I am unable to test the performance for both of them. What is the difference between these two? and which one would result in faster retrieval of documents and faster response?

Answer 1

The main difference between queries and filters has to do with scoring. Queries return documents with a relative ranked score for each document. Filters do not. This difference allows a filter to be faster for two reasons. First, it does not incur the cost of calculating the score for each document. Second, it can cache the results as it does not have to deal with possible changes in the score from moment to moment - it's just a boolean really, does the document match or not?

From the documentation:

Filters are usually faster than queries because:

they don’t have to calculate the relevance _score for each document —  the answer is just a boolean “Yes, the document matches the filter” or “No, the document does not match the filter”. the results from most filters can be cached in memory, making subsequent executions faster.

As a practical matter, the question is do you use the relevance score in any way? If not, filters are the way to go. If you do, filters still may be of use but should be used where they make sense. For instance, if you had a language field (let's say language: "EN" as an example) in your documents and wanted to query by language along with a relevance score, you would combine a query for the text search along with a filter for language. The filter would cache the document ids for all documents in english and then the query could be applied to that subset.

I'm over simplifying a bit, but that's the basics. Good places to read up on this:

http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl-filtered-query.html

http://www.elasticsearch.org/guide/en/elasticsearch/reference/0.90/query-dsl-filtered-query.html

http://exploringelasticsearch.com/searching_data.html

http://elasticsearch-users.115913.n3.nabble.com/Filters-vs-Queries-td3219558.html