[{parentId:1,"name":[{"language":"en-US","text":"Book"},{"language":"fr-CA","text":"livre"}],isActive:true/** and so many other fields*/},{parentId:1,"name":[{"language":"en-US","text":"Pen"}],isActive:true/** and so many other fields*/}]

db.collection.aggregate([{"$match":{"parentId":1}},{"$unwind":"$name"},{"$facet":{"french":[{"$match":{"name.language":"fr-CA"}}],"notFrench":[{"$match":{"name.language":"en-US"}}]}},{"$project":{"result":{"$cond":{"if":{"$eq":[{"$size":"$french"},0]},"then":"$notFrench","else":"$french"}}}}])