Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{arr:[{id:1,text:"foo"},{id:2,text:"bar"},]}]
Query
db.collection.aggregate([{$project:{elem1:{$arrayElemAt:["$arr",0]}}},{$project:{text1:"$elem1.text"}}])
Result