ElasticSearch 在排序操作时报错: Fielddata is disabled on text fields by default...

1. 异常信息:

   Fielddata is disabled on text fields by default. Set fielddata=true on [my_field] 
   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.
   

2. 解决办法:

   默认情况下 text 字段的 Fielddata 是禁用的。如果对 text 字段中的进行排序，汇总或访问值，则会看到上述异常。
   可以对 text 字段上启用 Fielddata 解决。

   curl -X PUT "localhost:9200/my_index/_mapping?pretty" -H 'Content-Type: application/json' -d'
   {
     "properties": {
       "my_field": { 
         "type":     "text",
         "fielddata": true
       }
     }
   }
   '
   

参考: https://www.elastic.co/guide/en/elasticsearch/reference/current/fielddata.html