Elasticsearch aggregation problem

 In the test Elasticsearch polymerization time reported an error. details as follows:

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

Error Messages

{
  "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": "wlvuJ0f_SsCxys6ZW5j7eA",
        "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
}

solution:

1, ElasticSearch5.x solution is open fielddata of:

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

2, version ElasticSearch6.x or 7.x open fielddata when:

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