关于ElasticSearch的聚类时出现fielddata=true问题

在ElasticSearch中默认fielddata默认是false的，因为开启Text的fielddata后对内存的占用很高

index：megacorp
type：employee

如果进行聚合查询时候：

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

返回错误码：

{
  "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. Alternatively use a keyword field instead."
      }
    ],
    "type" : "search_phase_execution_exception",
    "reason" : "all shards failed",
    "phase" : "query",
    "grouped" : true,
    "failed_shards" : [
      {
        "shard" : 0,
        "index" : "megacorp",
        "node" : "hDWX06IlTiu7gK3ybmsb-g",
        "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. Alternatively use a keyword field instead."
        }
      }
    ]
  },
  "status" : 400
}

提示：fielddata=true未开启
此时需要做的是:

curl -i -H "Content-Type:application/json" -XPUT 127.0.0.1:9200/your_index/_mapping/your_type/?pretty  -d'{"your_type":{"properties":{"your_field_name":{"type":"text","fielddata":true}}}}'

curl -i -H "Content-Type:application/json" -XPUT 127.0.0.1:9200/megacorp/_mapping/employee/?pretty  -d'{"employee":{"properties":{"interests":{"type":"text","fielddata":true}}}}'

interests指的是需要开启fielddata的field

此时再进行测试

 "aggregations" : {
    "all_interests" : {
      "doc_count_error_upper_bound" : 0,
      "sum_other_doc_count" : 0,
      "buckets" : [
        {
          "key" : "music",
          "doc_count" : 2
        },
        {
          "key" : "forestry",
          "doc_count" : 1
        },
        {
          "key" : "sports",
          "doc_count" : 1
        }
      ]
    }

就可以看出根据interests来进行聚类的查询结果，在这里就可以根据结果进行兴趣分析等

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