Elasticsearch 6.2.3版本 执行聚合报错 Fielddata is disabled on text fields by default

背景说明

执行《Elasticsearch 权威指南》的示例，在执行聚合查询的时候，报错 Fielddata is disabled on text fields by default.

1）聚合语句如下：

GET _search
{
  "aggs": {
    "all_interests": {
      "terms": { "field": "interests"}
    }
  }
}

2）报错信息如下：

{
  "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": "jbFtoSVqQAqfYhE5uTBFvw",
        "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
}

3）Kibana 的 Dev Tools 执行截图如下：

原因分析

Elasticsearch 5.x版本以后，对排序和聚合等操作，用单独的数据结构(fielddata)缓存到内存里了，默认是不开启的，需要单独开启。

具体请参考：fielddata

解决方案

1）执行如下语句，将 interests字段进行开启映射mapping：

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

2）Kibana 的 Dev Tools 中执行开启映射mapping语句，截图如下：

3）再次实行聚合语句，结果如下：

{
  "took": 455,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 3,
    "max_score": 1,
    "hits": [
      {
        "_index": "megacorp",
        "_type": "employee",
        "_id": "2",
        "_score": 1,
        "_source": {
          "first_name": "Jane",
          "last_name": "Smith",
          "age": 32,
          "about": "I like to collect rock albums",
          "interests": [
            "music"
          ]
        }
      },
      {
        "_index": "megacorp",
        "_type": "employee",
        "_id": "1",
        "_score": 1,
        "_source": {
          "first_name": "John",
          "last_name": "Smith",
          "age": 25,
          "about": "I love to go rock climbing",
          "interests": [
            "sports"
          ]
        }
      },
      {
        "_index": "megacorp",
        "_type": "employee",
        "_id": "3",
        "_score": 1,
        "_source": {
          "first_name": "Douglas",
          "last_name": "Fir",
          "age": 35,
          "about": "I like to build cabinets",
          "interests": [
            "forestry"
          ]
        }
      }
    ]
  },
  "aggregations": {
    "all_interests": {
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 0,
      "buckets": [
        {
          "key": "forestry",
          "doc_count": 1
        },
        {
          "key": "music",
          "doc_count": 1
        },
        {
          "key": "sports",
          "doc_count": 1
        }
      ]
    }
  }
}

4）Kibana 的 Dev Tools 中，执行效果截图如下：