While investigating SERVER-67539, we noticed that the documentation for showRecordId() has a stale example. There is more context in SERVER-67539 but I will explain the problem here as well. This pertains to the following docs page: https://www.mongodb.com/docs/manual/reference/method/cursor.showRecordId/.

At the bottom of the page, we have the following example:

You can project the added field $recordId, as in the following example:

db.collection.find( { a: 1 }, { $recordId: 1 } ).showRecordId()

This query returns only the _id field and the $recordId field in the matching documents:

{
"_id" : ObjectId("53908ccb18facd50a75bfbac"),
"$recordId" : NumberLong(168112)
}
{
"_id" : ObjectId("53908cd518facd50a75bfbad"),
"$recordId" : NumberLong(168176)
}

This used to be accurate, but the behavior changed in MongoDB 4.4 as part of PM-684. The server will now omit the "$recordId" field for this query:

MongoDB Enterprise > db.c.find({}, {$recordId: 1}).showRecordId()
{ "_id" : ObjectId("62fead4bee4c4666b602252e") }
{ "_id" : ObjectId("62fead4bee4c4666b6022530") }
{ "_id" : ObjectId("62fead4cee4c4666b6022532") }

We should either correct the example or delete it. The following query can be used instead against 4.4+ versions of the server to return results containing just the _id and $recordId fields:

MongoDB Enterprise > db.c.find({}, {_id: 1}).showRecordId()
{ "_id" : ObjectId("62fead4bee4c4666b602252e"), "$recordId" : NumberLong(1) }
{ "_id" : ObjectId("62fead4bee4c4666b6022530"), "$recordId" : NumberLong(2) }
{ "_id" : ObjectId("62fead4cee4c4666b6022532"), "$recordId" : NumberLong(3) }