Sort based on length of an array in elasticsearch

Question

There is a field where there is an array stored. I want to sort the documents based on the array length of that field.

Sample documents

document 1 = {
"countryCodes" : ["US","UK","UA","IN"]
}

document 2 ={
"countryCodes" : ["FR","SU","UG","UK","US"]
}

So, up on sort, the results should be showing document 2 first and then document 1.

Answer 1

There are two options here.

1. Use token count type as multi field in the mapping - This way another field would be stored as mutlti field which has the length of the array . You can learn more about it here.

2. Scripting - The same can be achieved using scripting too .

   { "sort": { "_script": { "script": "doc['countryCodes'].values.size()" } } }

Answer 2

For Elasticsearch 5.6.7 query should look like this:

GET index/_search
{
    "query": {
        "match_all": {}
    },
    "sort": {
        "_script": {
            "type" : "number",
            "script" : {
                "lang": "painless",
                "source": "doc.countryCodes.values.size()"
            },
            "order" : "desc"
        }
    }
}