Whenever I put a pipeline in $lookup I get zero comments from the merge

Whenever I put a pipeline in $lookup I get zero comments from the merge.

for example

"pipeline" :  [{"$sort" : {'date' : -1}}],

"pipeline" :  [{"$limit" : 1000}],

when I comment out the inner pipeline I get the correct comments, but can’t sort or limit…

{"$lookup": {
                "from" : 'comments',
                "localField" : '_id',
                "foreignField" : 'movie_id',
                # "pipeline" :  [{"$sort" : {'date' : -1}}],
                # "pipeline" :  [{"$limit" : 1000}],
                "as": 'comments'
            }}

You have to use another version of $lookup.

See https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/#join-conditions-and-subqueries-on-a-joined-collection