When matching multiple items in inner collections / document arrays, selecting with

{ 'innerCollection.$' : 1 }

only returns one of the matched element.

e.g.:
Doing

> db.testCollection.insert({ name : 'Albert', innerCollection : [

{memberId: 'red'}

,

{memberId : 'green'}

] })
> db.testCollection.insert({ name : 'Beatrice', innerCollection : [

{memberId: 'red'}

,

{memberId : 'blue'}

] })
> db.testCollection.insert({ name : 'Carl', innerCollection : [

{memberId: 'green'}

,

{memberId : 'blue'}

] })

> db.testCollection.find({ $and : [

{'innerCollection.memberId' : 'blue'}

,

{'innerCollection.memberId' : 'red'}

]},

{'innerCollection.$' : 1}

)
{ "_id" : ObjectId("5011c44a5748f01ae71d50d7"), "innerCollection" : [

{ "memberId" : "red" }

] }

properly finds the requested documents, but the innerCollection item only returns the element matching

{ 'innerCollection.memberId' : 'red' }

.