Syntax for function_score in Elastic Search - elasticsearch

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}
} ]
}
}