Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{"key":1,"contribs":"ALGOL"},{"key":2,"contribs":"Lisp"}]
Query
db.collection.find({$expr:{$cond:{if:{$size:[["ALGOL"]]},then:{$in:["$contribs",["ALGOL"]]},else:{}}}})
Result