elasticsearch学习笔记（十六）——Elasticsearch mget批量查询api实战

首先说明一下为什么需要批量查询操作？
假设一下比如说我们没有批量查询的操作，那么当我们获取数据的时候，就是一条一条的查询。设想一下我们要获取100条数据，那么就要发送100次请求，这个开销时很大的。但是有了批量查询的话，查询100条数据，就只需要发送一次网络请求就可以了，网络请求的性能开销缩减100倍。

下面是实战部分，演示一下一条一条查询与批量查询：
（1）一条一条查询

GET /test_index/_doc/1
{
  "_index" : "test_index",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 8,
  "_seq_no" : 7,
  "_primary_term" : 1,
  "found" : true,
  "_source" : {
    "test_field" : "test test",
    "name" : "test1"
  }
}
GET /test_index/_doc/2
{
  "_index" : "test_index",
  "_type" : "_doc",
  "_id" : "2",
  "_version" : 4,
  "_seq_no" : 3,
  "_primary_term" : 1,
  "found" : true,
  "_source" : {
    "test_field" : "test client 1",
    "name" : "test1"
  }
}

（2）mget批量查询

GET /_mget
{
  "docs": [
    {
      "_index": "test_index",
      "_id": 1
    },
    {
      "_index": "test_index",
      "_id": 2
    }
  ]
}
{
  "docs" : [
    {
      "_index" : "test_index",
      "_type" : "_doc",
      "_id" : "1",
      "_version" : 8,
      "_seq_no" : 7,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "test_field" : "test test",
        "name" : "test1"
      }
    },
    {
      "_index" : "test_index",
      "_type" : "_doc",
      "_id" : "2",
      "_version" : 4,
      "_seq_no" : 3,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "test_field" : "test client 1",
        "name" : "test1"
      }
    }
  ]
}