CODEWITHSUNDEEP
node.jsmongodbmongoosemongodb-queryaggregation-framework
Ashh
Ashh

Reputation: 46441

$lookup aggregation for nested array ids

I have Label, Conversations and Messages models...

Label contains Conversations id's... I have used $lookup which works for conversation

const conversation = await Label.aggregate([
    { $match: { _id: mongoose.Types.ObjectId("5abcb74bb59afe4310c60266") } },
    { $lookup: {
        from: 'conversations',
        localField: 'conversations',
        foreignField: '_id',
        as: "conversations"
      }
    }])

and gives output like 

[{ 
    _id: 5abcb74bb59afe4310c60266,
    name: 'Archive',
    value: 'archive',
    user: 5abc93a85d3914318cc8d3d7,
    conversations: [ [Object], [Object] ],
    __v: 0 
}]

Now I have messages inside conversations

[{ 
    _id: 5abe07717a978c41b270b1bc,
    messages: [ 5abe07717a978c41b270b1bd ],
    members: [ 5abc93a85d3914318cc8d3d7, 5abc9467b7c99332f0a6813c ],
    __v: 0
}]

So how do I apply $lookup for the messages fields which is inside

label -> conversations -> messasges

Thanks in advance

Upvotes: 0

Views: 463

Answers (1)

Webvoid
Webvoid

Reputation: 511

You will have to use $unwind on $conversations. This will cause your conversations array to explode and you will now have as much documents as conversations in your hands.

Then you should do your $lookup, and (if wanted) $group to fallback on what you had before $unwind

const conversation = await Label.aggregate([
    { $match: { _id: mongoose.Types.ObjectId("5abcb74bb59afe4310c60266") } },
    { $lookup: {
        from: 'conversations',
        localField: 'conversations',
        foreignField: '_id',
        as: "conversations"
        }
    },
    { $unwind: "$conversations" },
    {
        $lookup: {
        from: 'messages', 
        localField: 'conversations.messages',
        foreignField: '_id',
        as: 'myMessages'
        }
    }
])

Upvotes: 1

Related Questions