Elasticsearch：Fielddata is disabled on text fields by default. Set fielddate=true on...

今天在ES中执行cardinality时报出illegal_argument_exception，提示原因是Fielddata is disabled on text fields by default. Set fielddata=true on [policyno] 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.

//查询语句
{
	"query":{
		"match":{
			"sex":"1"
		}
	},
	"aggs":{
		"distinct_count":{
			"cardinality":{
				"field":"policyno"
			}
		}
	}
}

问题原因

ES中text类型的fielddata属性默认为false，因为text的cardinality可能非常大，造成内存占用过大

解决方案一（常用）

使用keyword查询

//查询语句
{
	"query":{
		"match":{
			"flag":"1"
		}
	},
	"aggs":{
		"counts":{
			"cardinality":{
				"field":"policyno.keyword"
			}
		}
	}
}

解决方案二

修改该字段的映射，设置fileddata属性为true

{
 	"properties": {
 		"policyno": { 
      		"type": "text",
      		"fielddata": true
    	}
  	}
}

解决方案三

重建索引，重新定义映射关系