Mongoid, aggregate models by name and number - ruby-on-rails

Question

I have model named Shop which has name, image. There is possibility that there will be multiple shops with the same name.
For example if I have these shops:
[{_id: "1", name: "Shop A", image: "ImageShopA.jpg"},
{_id: "2", name: "Shop A", image: "ImageShopA1.jpg"},
{_id: "3", name: "Shop B", image: "ImageShopB.jpg"},
{_id: "4", name: "Shop B", image: "ImageShopB1.jpg"},
{_id: "5", name: "Shop C", image: "ImageShopC.jpg"}]
I want to get this kind of result:
[{name: "Shop A", ids: ["1", "2"], image: "ImageShopA.jpg"},
{name: "Shop B", ids: ["3", "4"], image: "ImageShopB.jpg"},
{name: "Shop C", ids: ["5"], image: "ImageShopC.jpg"}]
It creates JSON Objects which has ids of grouped models which are grouped by name and get image of first found model.
Is it possible to do that with aggregation?

Answer 1

Yes, its possible. If you run the following aggregation pipeline in mongo shell with the given data sample
db.collection.aggregate([
{
"$sort": {
"_id": 1
}
},
{
"$group": {
"_id": "$name",
"ids": {
"$push": "$_id"
},
"image": {
"$first": "$image"
}
}
},
{
"$project": {
"name": "$_id", "ids": 1, "image": 1
}
}
])
you will get the desired results:
/* 0 */
{
"result" : [
{
"_id" : "Shop C",
"ids" : [
"5"
],
"image" : "ImageShopC.jpg",
"name" : "Shop C"
},
{
"_id" : "Shop B",
"ids" : [
"3",
"4"
],
"image" : "ImageShopB.jpg",
"name" : "Shop B"
},
{
"_id" : "Shop A",
"ids" : [
"1",
"2"
],
"image" : "ImageShopA.jpg",
"name" : "Shop A"
}
],
"ok" : 1
}
You would need to convert this to the appropriate ruby implemenation