Elasticsearch sort nested field

Question

I'm using Elasticsearch 6 with PHP.

My document has a nested field like this:

    "prices" : {
        "type" : "nested",
        "properties" : {
          "date" : {
            "type" : "date"
          },
          "duration" : {
            "type" : "short"
          },
          "persons" : {
            "type" : "short"
          },
          "pets" : {
            "type" : "short"
          },
          "price" : {
            "type" : "float"
          }
        }

Basically every document has a lot of prices, but I know that only one price per document will match the filter/query.

I use this to search and sort, adapted from the tutorial here: https://www.elastic.co/guide/en/elasticsearch/guide/current/nested-sorting.html (sorry for PHP array format):

$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'nested' => [
                'path' => 'prices',
                'query' => [
                    'bool' => [
                        'must' => [
                            ['match' => ['prices.duration' => 14]],
                            ['match' => ['prices.date' => '2018-09-01']],
                            ['match' => ['prices.pets' => 2]],
                            ['match' => ['prices.persons' => 2,]]
                        ]
                    ]
                ]
            ]
        ],
        'sort' => [
            'prices.price' => [
                'order' => 'asc',
                'mode' => 'min',
                'nested_filter' => [
                    'bool' => [
                        'must' => [
                            ['match' => ['prices.duration' => 14]],
                            ['match' => ['prices.date' => '2018-09-01']],
                            ['match' => ['prices.pets' => 2]],
                            ['match' => ['prices.persons' => 2]]
                        ]
                    ]
                ]
            ]
        ]
    ]
];

I get the correct results, but the documents are not sorted by price. How can I correctly sort them? The documents should be sorted by the one price that matches the filter.

Answer 1

Apparently I was using an old documentation. The correct sort part of the query above is:

    'sort' => [
        'prices.price' => [
            'order' => 'asc',
            'mode' => 'avg',
            'nested' => [
                'path' => 'prices',
                'filter' => [
                    'bool' => [
                        'must' => [
                            ['match' => ['prices.duration' => 14]],
                            ['match' => ['prices.date' => '2018-09-01']],
                            ['match' => ['prices.pets' => 2]],
                            ['match' => ['prices.persons' => 2]]
                        ]
                    ]
                ]
            ]
        ]
    ]