Corrected expresion $$REMOVE

[garnaizd]

Corrected expresion $$REMOVE to $REMOVE.

Error mesage is:

E QUERY [thread1] Error: command failed: {
"ok" : 0,
"errmsg" : "Use of undefined variable: REMOVE",
"code" : 17276,
"codeName" : "Location17276"
}

when executing:

db.prueba.aggregate( [ { $project: { title: 1, "author.first": 1, "author.last" : 1, "author.middle": { $cond: { if: { $eq: [ "", "$author.middle" ] }, then: "$$REMOVE", else: "$author.middle" } } } } ] )

---

This change is 

[steveren]

This code example can be found here: https://docs.mongodb.com/manual/reference/operator/aggregation/project/#conditionally-exclude-fields

I tested the complete example with MongoDB v3.6 and it executed correctly.

@garnaizd can you confirm your server and shell versions?

[garnaizd]

Maybe the error is for the version, because my version is MongoDB shell version v3.4.10

@steveren

[steveren]

That's correct. The REMOVE aggregation variable is new in version 3.6. https://docs.mongodb.com/manual/reference/aggregation-variables/#variable.REMOVE

@garnaizd

[garnaizd]

That's right. thank you @steveren.
Close this pull request.