ElasticSearch: aggregation on _score field?

Question

I would like to use the stats or extended_stats aggregation on the _score field but can\'t find any examples of this being done (i.e., seems like you can only u

Answer 1

doc.score doesn't seem to work anymore. Using _score seems to work perfectly.

Example:

{
    ...,
    "aggregations" : {
        "grades_stats" : { 
            "stats" : { 
                "script" : "_score" 
            } 
        }
    }
}

Answer 2

Note: The original answer is now outdated in terms of the latest version of Elasticsearch. The equivalent script using Groovy scripting would be:

{
    ...,
    "aggregations" : {
        "grades_stats" : { 
            "stats" : { 
                "script" : "_score" 
            } 
        }
    }
}

In order to make this work, you will need to enable dynamic scripting or, even better, store a file-based script and execute it by name (for added security by not enabling dynamic scripting)!

---

You can use a script and refer to the score using doc.score. More details are available in ElasticSearch's scripting documentation.

A sample stats aggregation could be:

{
    ...,
    "aggregations" : {
        "grades_stats" : { 
            "stats" : { 
                "script" : "doc.score" 
            } 
        }
    }
}

And the results would look like:

"aggregations": {
    "grades_stats": {
        "count": 165,
        "min": 0.46667441725730896,
        "max": 3.1525731086730957,
        "avg": 0.8296855776598959,
        "sum": 136.89812031388283
    }
}

A histogram may also be a useful aggregation:

"aggs": {
    "grades_histogram": {
        "histogram": {
            "script": "doc.score * 10",
            "interval": 3
        }
    }
}

Histogram results:

"aggregations": {
    "grades_histogram": {
        "buckets": [
            {
               "key": 3,
               "doc_count": 15
            },
            {
               "key": 6,
               "doc_count": 103
            },
            {
               "key": 9,
               "doc_count": 46
            },
            {
               "key": 30,
               "doc_count": 1
            }
        ]
    }
}