根据es官网的文档执行

GET /megacorp/employee/_search
{
  "aggs": {
    "all_interests": {
      "terms": { "field": "interests" }
    }
  }
}

这个例子时，报错

{
  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception","reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [interests] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory."
      }
    ],"type": "search_phase_execution_exception","reason": "all shards Failed","phase": "query","grouped": true,"Failed_shards": [
      {
        "shard": 0,"index": "megacorp","node": "-Md3f007Q3G6HtdnkXoRiA","reason": {
          "type": "illegal_argument_exception","reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [interests] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory."
        }
      }
    ],"caused_by": {
      "type": "illegal_argument_exception","reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [interests] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory."
    }
  },"status": 400
}

搜了一下应该是5.x后对排序，聚合这些操作用单独的数据结构(fielddata)缓存到内存里了，需要单独开启，官方解释在此fielddata

简单来说就是在聚合前执行如下操作

PUT megacorp/_mapping/employee/
{
  "properties": {
    "interests": { 
      "type":     "text","fielddata": true
    }
  }
}