MongoDB aggregation with multiple inter-related collections - mongodb

Question

I have the following collections;
users, user_roles, market_managers, program_markets, programs
I can export the data from mongoDB in CSV format and construct relational tables and run the following SQL statement to retrieve the data I need;
select u.name, ur.type, pm.code, p.program_name, p.shortnam, p.enddate, p.description
from users u, user_roles ur, market_managers mm, program_markets pm, programs p
where u.roles_0 = ur.id
and ur.type = 'CountryManager'
and u.id = mm.userid
and pm.programid = mm.programid
and pm.id = mm.marketid
and p.id = pm.programid;
How can I achieve the same results by writing native mongo syntax?
Here's a list of collections in scope:
users collection
{
"_id" : ObjectId("5b3f59c96e1c20d84e2b5ce5"),
"name" : "some_country_manager",
"roles" : [
"5b2a8df52b3a6f945d4e85fe"
]
}
user_roles collection
{
"_id" : ObjectId("5b430f9981f6a7382a24995b"),
"type" : "countryManager",
"name" : "Country Manager"
}
market_managers collection
{
"_id" : ObjectId("5894bcf60418700b70745fc9"),
"programId" : "5862c1d43b1a1b113a8a841f",
"marketId" : "5862c1d43b1a1b113a8a84a9",
"userId" : "5b3f59c96e1c20d84e2b5ce5"
}
program_markets collection
{
"_id" : ObjectId("5b43588689c117241c171e8c"),
"code" : "de",
"startDate" : "2018-07-09",
"endDate" : "2019-07-09"
}
programs collection
{
"_id" : ObjectId("5862c1d43b1a1b113a8a841f"),
"name" : "Test Program",
"shortname" : "TestP",
"status" : "planned",
"startDate" : "2018-07-09",
"endDate" : "2019-07-09",
"description" : "Test Program"
}

Answer 1

You can try below aggregation if you have mongodb 3.6 and above
Users.aggregate([
{ "$match": { "_id": mongoose.Types.ObjectId(id.id) } },
{ "$lookup": {
"from": UserRoles.collection.name,
"let": { "roles_0": "$roles_0" },
"pipeline": [
{ "$match": {
"$expr": { "$eq": [ "$_id", "$$roles_0" ] },
"type": "CountryManager"
}}
],
"as": "role"
}},
{ "$lookup": {
"from": MarketManagers.collection.name,
"let": { "user_id": "$_id" },
"pipeline": [
{ "$match": { "$expr": { "$eq": [ "$_id", "$$user_id" ] }}},
{ "$lookup": {
"from": Programs.collection.name,
"let": { "programid": "$programid" },
"pipeline": [
{ "$match": { "$expr": { "$eq": [ "$_id", "$$programid" ] }}}
],
"as": "programs"
}},
{ "$lookup": {
"from": ProgramManagers.collection.name,
"let": { "marketId": "$marketId" },
"pipeline": [
{ "$match": { "$expr": { "$eq": [ "$_id", "$$marketId" ] }}},
{ "$lookup": {
"from": Programs.collection.name,
"let": { "id": "$id" },
"pipeline": [
{ "$match": { "$expr": { "$eq": [ "$_id", "$$id" ] }}}
],
"as": "programs"
}}
],
"as": "programManagers"
}}
],
"as": "marketManagers"
}}
])