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db.collection.aggregate([{$set:{"rownum":{"$function":{"body":"function() {try {row_number+= 1;} catch (e) {row_number= 0;}return row_number;}","args":[],"lang":"js"}}}},{$bucket:{groupBy:"$rownum",/** Field to group by*/boundaries:[1,4,7,11,14,17,21,25],/** Boundaries for the buckets*/default:"Other",/** Bucket id for documents which do not fall into a bucket*/output:{/** Output for each bucket*/"countSUM":{$sum:"$count"},"averagePrice":{$avg:"$count"}}}}])