es聚合查询失败

查询命令

curl -X GET "localhost:9200/megacorp/employee/_search?pretty" -H 'Content-Type: application/json' -d'
{
  "aggs": {
    "all_interests": {
      "terms": { "field": "interests" }
    }
  }
}
'

抛出异常信息：

{
  "error" : {
    "root_cause" : [
      {
        "type" : "illegal_argument_exception",
        "reason" : "Text fields are not optimised for operations that require per-document field data like aggregations and sorting, so these operations are disabled by default. Please use a keyword field instead. Alternatively, set fielddata=true on [interests] in order to load field data by uninverting the inverted index. Note that this can use significant memory."
      }
    ],
    "type" : "search_phase_execution_exception",
    "reason" : "all shards failed",
    "phase" : "query",
    "grouped" : true,
    "failed_shards" : [
      {
        "shard" : 0,
        "index" : "megacorp",
        "node" : "EzyH308RT0iU4WNgOa2J5Q",
        "reason" : {
          "type" : "illegal_argument_exception",
          "reason" : "Text fields are not optimised for operations that require per-document field data like aggregations and sorting, so these operations are disabled by default. Please use a keyword field instead. Alternatively, set fielddata=true on [interests] in order to load field data by uninverting the inverted index. Note that this can use significant memory."
        }
      }
    ],
    "caused_by" : {
      "type" : "illegal_argument_exception",
      "reason" : "Text fields are not optimised for operations that require per-document field data like aggregations and sorting, so these operations are disabled by default. Please use a keyword field instead. Alternatively, set fielddata=true on [interests] in order to load field data by uninverting the inverted index. Note that this can use significant memory.",
      "caused_by" : {
        "type" : "illegal_argument_exception",
        "reason" : "Text fields are not optimised for operations that require per-document field data like aggregations and sorting, so these operations are disabled by default. Please use a keyword field instead. Alternatively, set fielddata=true on [interests] in order to load field data by uninverting the inverted index. Note that this can use significant memory."
      }
    }
  },
  "status" : 400
}

解决问题的连接：
https://www.elastic.co/guide/en/elasticsearch/reference/current/fielddata.html

从异常信息中可以看出，是因为我要聚合的字段【interests】没有进行优化，也类似没有加索引。没有优化的字段es默认是禁止聚合/排序操作的。所以需要将要聚合的字段添加优化

curl -X PUT "localhost:9200/megacorp/_mapping?pretty" -H 'Content-Type: application/json' -d'
{
  "properties": {
    "interests": { 
      "type":     "text",
      "fielddata": true
    }
  }
}
'

再次聚合查询一次，返回结果

{
  "took" : 3,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 3,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "megacorp",
        "_type" : "employee",
        "_id" : "1",
        "_score" : 1.0,
        "_source" : {
          "first_name" : "John",
          "last_name" : "Smith",
          "age" : 25,
          "about" : "I love to go rock climbing",
          "interests" : [
            "sports",
            "music"
          ]
        }
      },
      {
        "_index" : "megacorp",
        "_type" : "employee",
        "_id" : "2",
        "_score" : 1.0,
        "_source" : {
          "first_name" : "zxs",
          "last_name" : "xingsheng",
          "age" : 25,
          "about" : "I love to go shopping",
          "interests" : [
            "sports",
            "music"
          ]
        }
      },
      {
        "_index" : "megacorp",
        "_type" : "employee",
        "_id" : "3",
        "_score" : 1.0,
        "_source" : {
          "first_name" : "wll",
          "last_name" : "wanglingling",
          "age" : 25,
          "about" : "I love zxs",
          "interests" : [
            "sports",
            "music"
          ]
        }
      }
    ]
  },
  "aggregations" : {
    "all_interests" : {
      "doc_count_error_upper_bound" : 0,
      "sum_other_doc_count" : 0,
      "buckets" : [
        {
          "key" : "music",
          "doc_count" : 3
        },
        {
          "key" : "sports",
          "doc_count" : 3
        }
      ]
    }
  }
}