使用go从mongodb取数据时，如何分组数据？

Question

I have a collection named "myplace" It has the following fileds place_name, city, latitude, longitude.

Doc format

{
      "_id" : ObjectId("544a2147785b707b340ed6c7"),
      "latitude" : 12.36547,
      "longitude" : 1.235689,
      "place_name" : "some_place",
      "city" : "City1"
}
{
      "_id" : ObjectId("544a2147785b707b340ed6c7"),
      "latitude" : 12.36547,
      "longitude" : 1.235689,
      "place_name" : "some_place",
      "city" : "City3"
}
{
      "_id" : ObjectId("544a2147785b707b340ed6c7"),
      "latitude" : 12.36547,
      "longitude" : 1.235689,
      "place_name" : "some_place",
      "city" : "City1"
 }
 {
      "_id" : ObjectId("544a2147785b707b340ed6c7"),
      "latitude" : 12.36547,
      "longitude" : 1.235689,
      "place_name" : "some_place",
      "city" : "City2"
}
{
      "_id" : ObjectId("544a2147785b707b340ed6c7"),
      "latitude" : 12.36547,
      "longitude" : 1.235689,
      "place_name" : "some_place",
      "city" : "City2"
}

How can I group the data with same city? Meaning I need array of json result first array should contain all the data which having city1 second array conatins all the data which having city2 and so on

Answer 1

You could do it in Mongo itself more easily in my opinion. Use the aggregation framework.

db.yourCollection.aggregate([{$group:{_id: "$city", details:{$push: {latitude:  "$latitude",  longitude: "$longitude", place_name:"$place_name"}}}}])

I think this should work, I can't actually try it at the moment at work. hope it helps!