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db.collection.aggregate([{$match:{publishedAt:{$gte:ISODate("2000-01-01T00:00:00Z"),$lt:ISODate("2011-01-01T00:00:00Z")}}},{$group:{_id:{year:{$year:"$publishedAt"},category:"$category"},totalCount:{$count:{}}}},{$group:{"_id":"$_id.year","totalCount":{"$sum":"$totalCount"},"categoryCount":{"$push":{"k":{"$toString":"$_id.category"},"v":"$totalCount"}}}},{"$addFields":{"categoryCount":{"$arrayToObject":"$categoryCount"}}},{"$addFields":{"categoryCount":{"$mergeObjects":[{"0":0,"1":0,"2":0,"3":0,"4":0,"5":0},"$categoryCount"]}}},{"$addFields":{"categoryCount":{"$objectToArray":"$categoryCount"}}},{"$addFields":{"categoryCount":{"$map":{"input":"$categoryCount","as":"x","in":{"$mergeObjects":["$$x",{"k":{"$toInt":"$$x.k"}}]}}}}},{"$addFields":{"categoryCount":{"$sortArray":{"input":"$categoryCount","sortBy":{"$k":1}}}}},{"$addFields":{"categoryCount":"$categoryCount.v"}},{$sort:{_id:1}}])