Why am I getting “unrecognised argument to dateFromString: 'format'” despite having db version >3.6 which supports the aggregation

问题

I have some dates that are string formatted like this in chats:

"_id" : ObjectId("2bfd5d45348ef655b5236d93"),
"status" : "closed",
"context" : "Chats",
"chats" : {
    "time_initialized" : "2019-02-20T17:35:39.960284505Z",
    "time_responded" : "2019-02-20T17:42:06.691469546Z",
    "time_closed" : "2019-02-20T17:44:10.158421784Z"
}

My DB version in mongo is 3.6.5:

In the Mongo documentation, you can see below that the function dateFromString is supported:

Here's my code that is failing with:

"errmsg" : "Unrecognized argument to $dateFromString: format"

db.conversations.aggregate([
   {$match: {"context": "Chats", "status": "closed", 
   "chats.time_closed": {$exists: true}}},

   {$unwind: "$chats"},

  {$project: {chats:1, _id: 1, status: 1, 
  initialised_closed_duration: 
      {$divide: [
          {$subtract: [
              {$dateFromString: {dateString: "$chats.time_closed", format: "%Y-%m-%dT%H:%M:%S.000000000Z"}},{$dateFromString: {dateString: "$chats.time_initialized", format: "%Y-%m-%dT%H:%M:%S.000000000Z"}}]},60000]}}},
 {$limit: 5}]).pretty()

The point of my query is to get the date a chat is initialised and then closed, and work out the duration in minutes (hence dividing the millisecond date difference by 60,000)

Does anyone have any ideas about this?

回答1:

The operator was added in 3.6 but its signature changed in v4.

There was no "format" argument back in v3.6. The documentation for this version is available at https://docs.mongodb.com/v3.6/reference/operator/aggregation/dateFromString/

来源：https://stackoverflow.com/questions/54806248/why-am-i-getting-unrecognised-argument-to-datefromstring-format-despite-hav