Syntax for function_score in Elastic Search

Question

I am new to Elastic Search. I have indexed movie artists (actors and directors) in ElasticSearch and a simple text search works fine e.g if I search for 'steven' with the following syntax

{"query":
    {"query_string":
        {"query":"steven"}
    }
}

... I get the following results, which are fine :

1. Steven Conrad       - Popularity (from document) = 487 - elasticsearch _score = 3,2589545
2. Steven Knight       - Popularity (from document) = 487 - elasticsearch _score = 3,076738
3. Steven Waddington   - Popularity (from document) = 431 - elasticsearch _score = 2,4931839
4. Steven E. De Souza  - Popularity (from document) = 534 - elasticsearch _score = 2,4613905
5. Steven R. Monroe    - Popularity (from document) = 293 - elasticsearch _score = 2,4613905
6. Steven Mackintosh   - Popularity (from document) = 363 - elasticsearch _score = 2,2812681
7. Steven Wright       - Popularity (from document) = 356 - elasticsearch _score = 2,2812681
8. Steven Soderbergh   - Popularity (from document) = 5947 - elasticsearch _score = 2,270944
9. Steven Seagal       - Popularity (from document) = 1388 - elasticsearch _score = 2,270944
10. Steven Bauer        - Popularity (from document) = 714 - elasticsearch _score = 2,270944

However, as you can see above, I have a popularity numeric field in my document, and, when searching for 'steven', I would like the most popular artists (Steven Soderbergh, Steven Seagal ...) to come first.

Ideally, I'd like to sort the results above by popularity * _score

I am pretty sure I have to have use the function_score feature of Elastic Search but I can't figure out the exact syntax.

I've tried to do my "improved" search with the following syntax

{
  "query": {
    "custom_score": {
      "query": {
        "query_string": {
          "query": "steven"
        }
      },
      "script": "_score * doc['popularity']"
    }
  }
}

But I get an exception (extract from error message below :)

org.elasticsearch.search.query.QueryPhaseExecutionException: [my_index][4]: query[filtered(function score (_all:steven,function=script[_score * doc['popularity']], params [null]))->cache(_type:artist)],from[0],size[10]: Query Failed [Failed to execute main query]
  // ....
Caused by: java.lang.RuntimeException: uncomparable values <<1.9709579>> and <<org.elasticsearch.index.fielddata.ScriptDocValues$Longs@7c5b73bc>>
  // ... 
  ... 9 more
Caused by: java.lang.ClassCastException: org.elasticsearch.index.fielddata.ScriptDocValues$Longs cannot be cast to java.lang.Float
  at java.lang.Float.compareTo(Float.java:33)
  at org.elasticsearch.common.mvel2.math.MathProcessor.doOperationNonNumeric(MathProcessor.java:266)

I have the impression the syntax I use is incorrect

What should be the right syntax ? Or is there something else that I am missing ? Thanks a lot in advance

Edit My table mapping is defined as follows :

"mappings" : {
  "artist" : {
    "_all" : {
      "auto_boost" : true
    },
    "properties" : {
      "first_name" : {
        "type" : "string",
        "index" : "not_analyzed",
        "analyzer" : "standard"
      },
      "last_name" : {
        "type" : "string",
        "boost" : 2.0,
        "index" : "not_analyzed",
        "norms" : {
          "enabled" : true
        },
        "analyzer" : "standard"
      },
      "popularity" : {
        "type" : "integer"
      }
    }
  }
}

Answer 1

have you missed the .value near doc['...']?

this works for me (i stored integers without mapping):

$ curl -XPUT localhost:9200/test/test/a -d '{"name":"steven", "popularity": 666}'
{"_index":"test","_type":"test","_id":"a","_version":1,"created":true}

$ curl -XPUT localhost:9200/test/test/b -d '{"name":"steven", "popularity": 42}' 
{"_index":"test","_type":"test","_id":"b","_version":1,"created":true}

$ curl -XPOST localhost:9200/test/test/_search\?pretty -d '{ "query": { "custom_score": { "query": { "match_all": {}}, "script": "_score * doc[\"popularity\"].value" } } }'                                                                                                                                                 
{
  "took" : 83,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "failed" : 0
  },
  "hits" : {
    "total" : 2,
    "max_score" : 666.0,
    "hits" : [ {
      "_index" : "test",
      "_type" : "test",
      "_id" : "a",
      "_score" : 666.0, "_source" : {"name":"steven", "popularity": 666}
    }, {
      "_index" : "test",
      "_type" : "test",
      "_id" : "b",
      "_score" : 42.0, "_source" : {"name":"steven", "popularity": 42}
    } ]
  }
}