Elasticsearch, get average document length

Question

Is there any better way in elasticsearch (other than issuing a match all query and manually averaging over the length of all returned documents) to get the average document

Answer 1

Shot in the dark, but facets or aggregations combined with a script might do it.

{
    ...,

    "aggs" : {
        "avg_length" : { "avg" : { "script" : "doc['_all'].length" } }
    }
}