Mogodb Aggregation - node.js

Question

This is my user collection
{
"_id" : ObjectId("58e8cb640f861e6c40627a06"),
"actorId" : "665991",
"login" : "petroav",
"gravatar_id" : "",
"url" : "https://api.github.com/users/petroav",
"avatar_url" : "https://avatars.githubusercontent.com/u/665991?"
}
This is my repo collection
{
"_id" : ObjectId("58e8cb640f861e6c40627a07"),
"repoId" : "28688495",
"name" : "petroav/6.828",
"url" : "https://api.github.com/repos/petroav/6.828"
}
This is my events collections
{
"_id" : ObjectId("58e8cb640f861e6c40627a08"),
"eventId" : "2489651045",
"type" : "CreateEvent",
"actorLogin" : "petroav",
"repoId" : "28688495",
"eventDate" : ISODate("2015-01-01T15:00:00.000+0000"),
"public" : true
}
I am trying to do following queries on above data
Return list of all repositories with their top contributor
Find the repository with the highest number of events from an actor (by login). If multiple repos have the same number of events, return the one with the latest event.
Return actor details and list of contributed repositories by login
I tried 3 one by doing this
db.events.aggregate(
[ {
$match:{"actorLogin":"petroav"}
},
{
$lookup:{
from:"repos",
localField:"repoId",
foreignField:"repoId",
as:"Repostory"
}
},
{
$group:{ _id : "$Repostory", repo: { $push: "$$ROOT" } }
}
]
).pretty()
Please help. I am new to mongodb.

Answer 1

These should work, you may have to update some of the variable names if they don't match your code exactly. Because you are using actorLogin and repoId as references instead of _id, you likely want to create indexes for the fields to help with performance.
Also you may want to add a $project stage at the end of these pipelines if you want to clean up the final formats, remove extra fields, rename fields, etc..
For Number 1
db.repos.aggregate(
[
{
$lookup:{
from:"events",
localField:"repoId",
foreignField:"repoId",
as:"Event"
}
},{
$unwind:"$Event"
},
{
$group:{
_id : {repo: "$_id", user: "$Event.actorLogin" },
contributionCount: { $sum:1 },//number of times logged in
}
},
{
$sort: {
contributionCount: -1
}
},{
$group:{
_id: {repo:'$_id.repo'},
contributionCount: {$first: '$contributionCount' },
actorLogin: {$first: '$_id.user' }
}
}
]
).then(console.log)
For Number 2
db.events.aggregate(
[ {
$match:{"actorLogin":"petroav"}
},
{
$lookup:{
from:"repos",
localField:"repoId",
foreignField:"repoId",
as:"Repostory"
}
},{
$unwind:"$Repostory"
},
{
$group:{
_id : "$Repostory",
loginCount: { $sum:1 },//number of times logged in
lastLoginDate: {$max:'$eventDate'} //largest ISODate for the repo
}
},
{
$sort: {
loginCount: -1,
date: -1
}
},
{limit:1}
]
).then(console.log)
For number 3
db.user.aggregate(
[
{
$match:{"actorLogin":"petroav"}
},
{
$lookup:{
from:"events",
localField:"actorLogin",
foreignField:"actorLogin",
as:"Events"
}
},{
$unwind:"$Events"
},
{
$lookup:{
from:"repos",
localField:"Events.repoId",
foreignField:"repoId",
as:"Repostory"
}
},{
$unwind:"$Repostory"
},{
$group: {
_id:'$actorLogin',
user: {$first:'$$ROOT'}
repos: {$addToSet:'$Repostory'}
}
}
]
).then(console.log)