Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{"type":["admin","teacher","student"]},{"_id":ObjectId("5eaaeedd00101108e1123453"),"type":["student"],}]
Query
db.collection.find({$expr:{$gt:[{$size:"$type"},1]}})
Result