elasticsearch 深入 —— Top Hits Aggregation
Top Hits Aggregation
top_hits指标聚合器跟踪正在聚合的最相关文档。 此聚合器旨在用作子聚合器，以便可以按桶聚合最匹配的文档。
top_hits聚合器可以有效地用于通过桶聚合器按特定字段对结果集进行分组。 一个或多个存储桶聚合器确定结果集被切入的属性。
选项
from- 要获取的第一个结果的偏移量。size- 每个桶返回的最大匹配匹配数的最大数量。默认情况下，返回前三个匹配的匹配。sort- 如何对最匹配的匹配进行排序。默认情况下，命中按主查询的分数排序。
Supported per hit features 每个匹配功能支持
top_hits聚合返回常规搜索命中，因为可以支持许多每个命中功能：
- Highlighting
- Explain
- Named filters and queries
- Source filtering
- Stored fields
- Script fields
- Doc value fields
- Include versions
实例
下面来看看具体的例子，就知道怎么回事了，使用起来很简单。
- 先准备索引和数据，这里以菜谱为例，name：菜谱名，type 为菜系，rating 为用户的累积平均评分
PUT recipes
POST /recipes/type/_mapping
{
"properties": {
"name":{
"type": "text"
},
"rating":{
"type": "float"
},"type":{
"type": "keyword"
}
}
}
/recipes/_bulk
{ "index": { "_index": "recipes", "_type": "type"}}
{"name":"清蒸鱼头","rating":1,"type":"湘菜"}
{ "index": { "_index": "recipes", "_type": "type"}}
{"name":"剁椒鱼头","rating":2,"type":"湘菜"}
{ "index": { "_index": "recipes", "_type": "type"}}
{"name":"红烧鲫鱼","rating":3,"type":"湘菜"}
{ "index": { "_index": "recipes", "_type": "type"}}
{"name":"鲫鱼汤（辣）","rating":3,"type":"湘菜"}
{ "index": { "_index": "recipes", "_type": "type"}}
{"name":"鲫鱼汤（微辣）","rating":4,"type":"湘菜"}
{ "index": { "_index": "recipes", "_type": "type"}}
{"name":"鲫鱼汤（变态辣）","rating":5,"type":"湘菜"}
{ "index": { "_index": "recipes", "_type": "type"}}
{"name":"广式鲫鱼汤","rating":5,"type":"粤菜"}
{ "index": { "_index": "recipes", "_type": "type"}}
{"name":"鱼香肉丝","rating":2,"type":"川菜"}
{ "index": { "_index": "recipes", "_type": "type"}}
{"name":"奶油鲍鱼汤","rating":2,"type":"西菜"}
- 现在我们看看普通的查询效果是怎么样的，搜索关键字带“鱼”的菜，返回3条数据
POST recipes/type/_search
{
"query": {"match": {
"name": "鱼"
}},"size": 3
}
全是湘菜，我的天，最近上火不想吃辣，这个第一页的结果对我来说就是垃圾，如下：
{
"took": 2,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 9,
"max_score": 0.26742277,
"hits": [
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHYF_OA-dG63Txsd",
"_score": 0.26742277,
"_source": {
"name": "鲫鱼汤（变态辣）",
"rating": 5,
"type": "湘菜"
}
},
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHXO_OA-dG63Txsa",
"_score": 0.19100356,
"_source": {
"name": "红烧鲫鱼",
"rating": 3,
"type": "湘菜"
}
},
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHWy_OA-dG63TxsZ",
"_score": 0.19100356,
"_source": {
"name": "剁椒鱼头",
"rating": 2,
"type": "湘菜"
}
}
]
}
}
- 我们再看看，这次我想加个评分排序，大家都喜欢的是那些，看看有没有喜欢吃的，执行查询：
POST recipes/type/_search
{
"query": {"match": {
"name": "鱼"
}},"sort": [
{
"rating": {
"order": "desc"
}
}
],"size": 3
}
结果稍微好点了，不过3个里面2个是湘菜，还是有点不合适，结果如下：
{
"took": 1,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 9,
"max_score": null,
"hits": [
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHYF_OA-dG63Txsd",
"_score": null,
"_source": {
"name": "鲫鱼汤（变态辣）",
"rating": 5,
"type": "湘菜"
},
"sort": [
5
]
},
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHYW_OA-dG63Txse",
"_score": null,
"_source": {
"name": "广式鲫鱼汤",
"rating": 5,
"type": "粤菜"
},
"sort": [
5
]
},
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHX7_OA-dG63Txsc",
"_score": null,
"_source": {
"name": "鲫鱼汤（微辣）",
"rating": 4,
"type": "湘菜"
},
"sort": [
4
]
}
]
}
}
- 现在我知道了，我要看看其他菜系，这家不是还有西餐、广东菜等各种菜系的么，来来，帮我每个菜系来一个菜看看，换 terms agg 先得到唯一的 term 的 bucket，再组合 top_hits agg，返回按评分排序的第一个 top hits，有点复杂，没关系，看下面的查询就知道了：
GET recipes/type/_search
{
"query": {
"match": {
"name": "鱼"
}
},
"sort": [
{
"rating": {
"order": "desc"
}
}
],"aggs": {
"type": {
"terms": {
"field": "type",
"size": 10
},"aggs": {
"rated": {
"top_hits": {
"sort": [{
"rating": {"order": "desc"}
}],
"size": 1
}
}
}
}
},
"size": 0,
"from": 0
}
看下面的结果，虽然 json 结构有点复杂，不过总算是我们想要的结果了，湘菜、粤菜、川菜、西菜都出来了，每样一个，不重样：
{
"took": 4,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 9,
"max_score": 0,
"hits": []
},
"aggregations": {
"type": {
"doc_count_error_upper_bound": 0,
"sum_other_doc_count": 0,
"buckets": [
{
"key": "湘菜",
"doc_count": 6,
"rated": {
"hits": {
"total": 6,
"max_score": null,
"hits": [
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHYF_OA-dG63Txsd",
"_score": null,
"_source": {
"name": "鲫鱼汤（变态辣）",
"rating": 5,
"type": "湘菜"
},
"sort": [
5
]
}
]
}
}
},
{
"key": "川菜",
"doc_count": 1,
"rated": {
"hits": {
"total": 1,
"max_score": null,
"hits": [
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHYr_OA-dG63Txsf",
"_score": null,
"_source": {
"name": "鱼香肉丝",
"rating": 2,
"type": "川菜"
},
"sort": [
2
]
}
]
}
}
},
{
"key": "粤菜",
"doc_count": 1,
"rated": {
"hits": {
"total": 1,
"max_score": null,
"hits": [
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHYW_OA-dG63Txse",
"_score": null,
"_source": {
"name": "广式鲫鱼汤",
"rating": 5,
"type": "粤菜"
},
"sort": [
5
]
}
]
}
}
},
{
"key": "西菜",
"doc_count": 1,
"rated": {
"hits": {
"total": 1,
"max_score": null,
"hits": [
{
"_index": "recipes",
"_type": "type",
"_id": "AVoESHY3_OA-dG63Txsg",
"_score": null,
"_source": {
"name": "奶油鲍鱼汤",
"rating": 2,
"type": "西菜"
},
"sort": [
2
]
}
]
}
}
}
]
}
}
}