路由（routing）

Elasticsearch写入文档时，文档会通过一个公式路由到一个索引中的一个分片上。默认公式如下：

shard_num = hash(_routing) % num_primary_shards

_routing字段的取值，默认是_id字段，可以根据业务场景设置经常查询的字段作为路由字段。例如可以考虑将用户id、地区作为路由字段，查询时可以过滤不必要的分片，加快查询速度。

安全模式下写入时指定路由：

curl -XPUT --tlsv1.2 --negotiate -k -u : "https://ip:httpport/my_index/my_type/1?routing=user1&refresh=true" -H 'Content-Type: application/json' -d' 
{
  "title": "This is a document"
}'

安全模式下查询时不指定路由示例：

curl -XGET --tlsv1.2 --negotiate -k -u : "https://ip:httpport/my_index/_search?pretty" -H 'Content-Type: application/json' -d'
{
  "query": {
    "match": {
      "title": "document"
    }
  }
}'

需要查询所有的分片，返回结果：

{
  "took" : 5,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 0.2876821,
    "hits" : [
      {
        "_index" : "my_index",
        "_type" : "my_type",
        "_id" : "1",
        "_score" : 0.2876821,
        "_routing" : "user1",
        "_source" : {
          "title" : "This is a document"
        }
      }
    ]
  }
}

安全模式下查询时指定路由示例：

curl -XGET --tlsv1.2 --negotiate -k -u : "https://ip:httpport/my_index/_search?routing=user1&pretty" -H 'Content-Type: application/json' -d'
{
  "query": {
    "match": {
      "title": "document"
    }
  }
}'

查询时只需要查询一个分片，查询结果：

{
  "took" : 8,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 0.2876821,
    "hits" : [
      {
        "_index" : "my_index",
        "_type" : "my_type",
        "_id" : "1",
        "_score" : 0.2876821,
        "_routing" : "user1",
        "_source" : {
          "title" : "This is a document"
        }
      }
    ]
  }
}