Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{"_id":1,"data":[-1,100,150,200,-1,-1]}]
Query
db.collection.aggregate([{$project:{indices:{$filter:{input:{$range:[0,{$size:"$data"}]},cond:{$eq:[{$arrayElemAt:["$data","$$this"]},-1]}}}}}])
Result