Average size of documents in ElasticSearch

Elastic Stack Elasticsearch
1

Can I use a query like that to calculate the average size of documents in indexes if I don't have the _size enable at index level but I have the _source enabled?

{
  "query" : {"match_all" : {}},
  "aggs":{
    "avg_length" : { "avg" : { "script" : "_source.toString().length()"}}
  }
}

Act
Well, this is the char count. If strings are UTF-8 a think I can get the byte count with


  "query" : {"match_all" : {}},
  "aggs":{
    "avg_length" : { "avg" : { "script" : "_source.toString().getBytes(\"UTF-8\").length"}}
  }
}

Thanks