Text fields are not optimised for operations that require per-document field data like aggregations and sorting,

es执行如下命令报错 ``` #脚本字段 这个执行报错没明白啥原因 GET wenda_content/_search { "script_fields": { "new_field": { "script": { "lang": "painless", "source": "doc['title'].value+'hello'" } } }, "query": { "match_all": {} } } ``` 报如下错误: > Text fields are not optimised for operations that require per-document field data like aggregations and sorting, so these operations are disabled by default. Please use a keyword field instead. Alternatively, set fielddata=true on [title] in order to load field data by uninverting the inverted index. Note that this can use significant memory. 谷歌翻译如下： > 文本字段并未针对需要每个文档字段数据的操作（例如聚合和排序）进行优化，因此默认情况下将禁用这些操作。 请改用关键字字段。 或者，在[title]上设置fielddata = true，以通过反转取反的索引来加载字段数据。 请注意，这可能会占用大量内存。 没明白啥意思？求解？