1.Elasticsearch:No handler for type [string] declared on field[XXX]
Description of the problem: Elasticsearch has introduced text and keyword since 5.X. The keyword is suitable for wordless fields. It can only be completely matched when searching. At this time, the string is still retained. In 6.X, strings are completely removed. In addition, the value of "index" can only be a boolean variable.
Solution: {"type":"text","index":false}