ElasticSearch中nested索引类型

参考官网：https://www.elastic.co/guide/en/elasticsearch/reference/current/nested.html#nested-fields-array-objects

The nested type is a specialised version of the object data type that allows arrays of objects to be indexed in a way that they can be queried independently of each other.

Elasticsearch has no concept of inner objects. Therefore, it flattens object hierarchies into a simple list of field names and values. For instance, consider the following document:

# 添加索引数据，此时索引类型没有在mapping中指定为nested
PUT my-index-000001/_doc/1
{
  "group" : "fans",
  "user" : [ 
    {
      "first" : "John",
      "last" :  "Smith"
    },
    {
      "first" : "Alice",
      "last" :  "White"
    }
  ]
}

The user field is dynamically added as a field of type object.

# 查询数据
GET my-index-000001/_search
{
  "query": {
    "bool": {
      "must": [
        { "match": { "user.first": "Alice" }},
        { "match": { "user.last":  "White" }}
      ]
    }
  }
}

The previous document would be transformed internally into a document that looks more like this:

{
  "group" :        "fans",
  "user.first" : [ "alice", "john" ],
  "user.last" :  [ "smith", "white" ]
}

The user.first and user.last fields are flattened into multi-value fields, and the association between alice and white is lost. This document would incorrectly match a query for alice AND smith:

# 创建索引,指定索引类型中user类型为nested
PUT my-index-000001
{
  "mappings": {
    "properties": {
      "user": {
        "type": "nested" 
      }
    }
  }
}

# 添加数据到索引
PUT my-index-000001/_doc/1
{
  "group" : "fans",
  "user" : [
    {
      "first" : "John",
      "last" :  "Smith"
    },
    {
      "first" : "Alice",
      "last" :  "White"
    }
  ]
}

# 查询索引数据
GET my-index-000001/_search
{
  "query": {
    "nested": {
      "path": "user",
      "query": {
        "bool": {
          "must": [
            { "match": { "user.first": "Alice" }},
            { "match": { "user.last":  "Smith" }} 
          ]
        }
      }
    }
  }
}

# 查询索引数据
GET my-index-000001/_search
{
  "query": {
    "nested": {
      "path": "user",
      "query": {
        "bool": {
          "must": [
            { "match": { "user.first": "Alice" }},
            { "match": { "user.last":  "White" }} 
          ]
        }
      },
      "inner_hits": { 
        "highlight": {
          "fields": {
            "user.first": {}
          }
        }
      }
    }
  }
}