Custom sorting in Elasticsearch

Question

Does anyone know if it's possible to custom sort in elasticsearch?

I have a sort on the category field. Which groups all of the records together by category. This works great.

However could you then give the sort a list e.g cars, books, food.

It would then show the cars first, then books and finally food?

Answer 1

You can use a function_score query, something like this:

{
    "query": {
        "function_score": {
          "query": { "match_all": {} },
          "boost": "5", 
          "functions": [
              {
                  "filter": { "match": { "category": "cars" } },
                  "weight": 100
              },
              {
                  "filter": { "match": { "category": "books" } },
                  "weight": 50
              },
              {
                  "filter": { "match": { "category": "food" } },
                  "weight": 1
              }
          ],
          "score_mode": "max",
          "boost_mode": "replace"
        }
    }
}

Where you, of course, put whichever query you are using now instead of the match_all query, and leave off the sort (the default is by score, which is what you want here).

This is replacing the score elasticsearch normally generates, with a custom score for each category. You could experiment with other boost_mode in order to have a reasonable ranking within the categories. In case you need to understand what is happening with the scoring, you can add "explain": true to the query at the top level.

Answer 2

You can use custom script for your own scoring.

More details at in Script Based Sorting section: https://www.elastic.co/guide/en/elasticsearch/reference/5.5/search-request-sort.html