[{"_id":NumberLong(409),"Parsed":{"FileId":"421462559","MessageId":"123","Fields":[{"SchemaName":"xxx","Type":0,"Value":6},{"SchemaName":"yyy","Type":0,"Value":5}]}},{"_id":NumberLong(510),"Parsed":{"FileId":"421462559","MessageId":"123","Fields":[{"SchemaName":"xxx","Type":0,"Value":10},{"SchemaName":"yyy","Type":0,"Value":20}]}}]

db.collection.aggregate([{$match:{"Parsed.Fields.SchemaName":"xxx"}},{$unwind:"$Parsed.Fields"},{$match:{"Parsed.Fields.SchemaName":"xxx"}},{$group:{_id:null,count:{$sum:1},max:{$max:"$Parsed.Fields.Value"},min:{$min:"$Parsed.Fields.Value"},avg:{$avg:"$Parsed.Fields.Value"}}}])