es - elasticsearch mapping - parameters - fielddata

世界上并没有完美的程序，但是我们并不因此而沮丧，因为写程序就是一个不断追求完美的过程。

问 ：fielddata有什么特点？
答 ：

问 ：fielddata如何使用？
答 ：

# fielddata
PUT /fielddata_test
{
  "mappings" : {
    "properties" : {
      "content" : {
        "type"      : "text",
        "fielddata" : true
      }
    }
  }
}

# 索引
POST /fielddata_test/_doc/1
{
  "content" : "hello good"
}

# 搜索 - 聚合
GET /fielddata_test/_search
{
  "aggs" : {
    "content_aggs" : {
      "terms": {
        "field" : "content",
        "size"  : 10
      }
    }
  }
}

# 结果
{
  "took" : 195,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 1,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "fielddata_test",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 1.0,
        "_source" : {
          "content" : "hello good"
        }
      }
    ]
  },
  "aggregations" : {
    "content_aggs" : {
      "doc_count_error_upper_bound" : 0,
      "sum_other_doc_count" : 0,
      "buckets" : [
        {
          "key" : "good",
          "doc_count" : 1
        },
        {
          "key" : "hello",
          "doc_count" : 1
        }
      ]
    }
  }
}