node.js - Merge two MongoDB aggregates into one pipeline -

i have collection of population census , still don't dominate “aggregate” function results 1 query.

the collection has this format (plus iso 8601 timestamp). way, each time census conducted can register current ages , counts (which can add/modify/delete previous ages).

now have 2 “aggregate” queries to return this:

1. get avg, max, min of registries in db.
2. get each age , show total (“sum”) of people age.

however need results 1 “aggregate” query, pipeline difficult me, , cannot statistics , “unwind” population sums…

any on how merge 2 queries, please? thank in advance!

try following aggregation pipeline, should give result of 2 queries:

db.collection('population').aggregate([     {         "$unwind": "$population"     },     {         "$group": {             "_id": 0,             "doc": {                 "$push": "$$root"             },             "average_age": {                 "$avg": "$population.age"             },             "max_age": {                 "$max": "$population.age"             },             "min_age": {                 "$min": "$population.age"             },             "average_population": {                 "$avg": "$population.count"             },             "max_population": {                 "$max": "$population.count"             },             "min_population": {                 "$min": "$population.count"             }         }     },     {         "$unwind": "$doc"     },     {         "$group": {             "_id": "$doc.population.age",             "sum": { "$sum": "$doc.population.count" },             "average_age": { "$first": "$average_age"},             "max_age": { "$first": "$max_age"},             "min_age": { "$first": "$min_age"},             "average_population": { "$first": "$average_population"},             "max_population": { "$first": "$max_population"},             "min_population": { "$first": "$min_population"}         }     } ])