Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{_id:{"foo":"abc"},"time":[],"bar":[[],[]]}]
Query
db.collection.aggregate([{$replaceRoot:{newRoot:{$mergeObjects:[{$arrayToObject:[[{k:"$_id.foo",v:"$bar"}]]},"$$ROOT"]}}},{$project:{bar:0}}])
Result