MongoDB full-text index error, v3.4

  mongodb, question 
> db.test2.insert({string:"aa bb cc"});
 WriteResult({ "nInserted" : 1 })
 > db.test2.insert({string:"aa 88 99"});
 WriteResult({ "nInserted" : 1 })
 > db.test2.ensureIndex({'string':"text"});

Error after setting ensureIndex:

{
 "ok" : 0,
 "errmsg" : "Index: { v: 2, key: { _fts: \"text\", _ftsx: 1 }, name: \"string_text\", ns: \"test2.test2\", weights: { string: 1 }, default_language: \  "english\", language_override: \"language\", textIndexVersion: 3 } already exists with different options: { v: 2, key: { _fts: \"text\", _ftsx: 1 },   name: \"post_text_text\", ns: \"test2.test2\", weights: { post_text: 1 }, default_language: \"english\", language_override: \"language\", textIndexVersion: 3 }",
 "code" : 85,
 "codeName" : "IndexOptionsConflict"
 }

First inv3.4Version this methodensureIndex()The name has been changed. Today’s other name iscreateIndex().Document

Secondly, the usage of this method is

db.col.ensureIndex({"title":1})

Follow behind1Or ..-1On behalf of the sorting method, can also betextIs a full-text index or a geographic location index2dOr2dphere. (according to the @Mongoing Chinese community’s answer, add a few words)

Chinese document
English document

The above meaning should be that you have already set it and the index already exists. Conflict.