Alternative query

Working with Data
,
4

My 2 cents.

I do not think that the following is possible.

The $match query the field critics which is the result of the $lookup. So it cannot be done before.

You use case seems overly simplistic. It looks like you want to somehow process the clinics on an ordered way using the category. I would implement a use-case like that by aggregation on the clinics and $lookup on categories.

pipeline = [
    { "$sort" : {
        "category" : 1
    } } ,
    { "$lookup" : {
        "from" : "categories" ,
        "localField" : "category" ,
        "foreignField" : "_id" ,
        "as" : "category"
    } }
] ;
db.clinics.aggregate( pipe ) ;

It is kind of a $group but without the risking the 16MB limit due to a massive array.

One caveat is that the category data is duplicated in the output. A $project could be used in the $lookup pipeline to reduce this.

Please read Formatting code and log snippets in posts before posting new code or documents. We cannot cut-n-paste code or documents from an image so it makes experimenting and replying slower than it could.

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