Database

[{"seriesId":{"seriesId":"77678ca1-31db-4cec-a042-68a3053b92c6"},"testStepId":{"testStepId":"c152415b-2392-4c2b-af74-51a4973bd257"},"measurement":{"startTime":{"$date":"2020-07-07T12:40:49.782Z"},"endTime":{"$date":"2020-07-07T12:42:19.782Z"}},"dataPoints":[{"timeStamp":{"$date":"2020-07-07T12:41:09.782Z"},"value":"Value_1_1"},{"timeStamp":{"$date":"2020-07-07T12:41:29.782Z"},"value":"Value_1_2"},{"timeStamp":{"$date":"2020-07-07T12:41:39.782Z"},"value":"Value_1_3"},{"timeStamp":{"$date":"2020-07-07T12:42:19.782Z"},"value":"Value_2_11"}]},{"seriesId":{"seriesId":"77678ca1-31db-4cec-a042-68a3053b92c6"},"testStepId":{"testStepId":"c152415b-2392-4c2b-af74-51a4973bd257"},"measurement":{"startTime":{"$date":"2020-07-07T12:40:49.782Z"},"endTime":{"$date":"2020-07-07T12:42:19.782Z"}},"dataPoints":[{"timeStamp":{"$date":"2020-07-07T12:41:09.782Z"},"value":"Value_1_1"},{"timeStamp":{"$date":"2020-07-07T12:41:29.782Z"},"value":"Value_1_2"},{"timeStamp":{"$date":"2020-07-07T12:41:39.782Z"},"value":"Value_1_3"},{"timeStamp":{"$date":"2020-07-07T12:42:19.782Z"},"value":"Value_2_11"}]}]

Query

db.collection.aggregate([{$group:{_id:null,count:{$sum:1},all:{$push:"$$ROOT"}}},{$unwind:"$all"},{$replaceWith:{$mergeObjects:["$all",{dataPoints:{$map:{input:{$range:[0,{"$size":"$all.dataPoints"},{$ceil:{$divide:[{$multiply:[{"$size":"$all.dataPoints"},"$count"]},1000]}}]},as:"index",in:{$arrayElemAt:["$all.dataPoints","$$index"]}}}}]}}])

Result