读《深入理解Elasticsearch》点滴-聚合-top_hits

以下是官网手册（部分）（v5.1）

直接直接看官网手册

https://www.elastic.co/guide/en/elasticsearch/reference/5.1/search-aggregations-metrics-top-hits-aggregation.html

Top hits Aggregationedit

A top_hits metric aggregator keeps track of the most relevant document being aggregated. This aggregator is intended to be used as a sub aggregator, so that the top matching documents can be aggregated per bucket.

The top_hits aggregator can effectively be used to group result sets by certain fields via a bucket aggregator. One or more bucket aggregators determines by which properties a result set get sliced into.

Optionsedit

• from - The offset from the first result you want to fetch.
• size - The maximum number of top matching hits to return per bucket. By default the top three matching hits are returned.
• sort - How the top matching hits should be sorted. By default the hits are sorted by the score of the main query.

Supported per hit featuresedit

The top_hits aggregation returns regular search hits, because of this many per hit features can be supported:

• Highlighting
• Explain
• Named filters and queries
• Source filtering
• Stored fields
• Script fields
• Doc value fields
• Include versions

Exampleedit

In the following example we group the questions by tag and per tag we show the last active question. For each question only the title field is being included in the source.

{
    "aggs": {
        "top-tags": {
            "terms": {
                "field": "tags",
                "size": 3
            },
            "aggs": {
                "top_tag_hits": {
                    "top_hits": {
                        "sort": [
                            {
                                "last_activity_date": {
                                    "order": "desc"
                                }
                            }
                        ],
                        "_source": {
                            "includes": [
                                "title"
                            ]
                        },
                        "size" : 1
                    }
                }
            }
        }
    }
}

Possible response snippet:

"aggregations": {
  "top-tags": {
     "buckets": [
        {
           "key": "windows-7",
           "doc_count": 25365,
           "top_tags_hits": {
              "hits": {
                 "total": 25365,
                 "max_score": 1,
                 "hits": [
                    {
                       "_index": "stack",
                       "_type": "question",
                       "_id": "602679",
                       "_score": 1,
                       "_source": {
                          "title": "Windows port opening"
                       },
                       "sort": [
                          1370143231177
                       ]
                    }
                 ]
              }
           }
        },
        {
           "key": "linux",
           "doc_count": 18342,
           "top_tags_hits": {
              "hits": {
                 "total": 18342,
                 "max_score": 1,
                 "hits": [
                    {