使用$ group两次的Mongodb Aggregate

Question

我在mongo中有一堆文件,结构如下:

{
    "_id" : "",
    "number" : 2,
    "colour" : {
        "_id" : "",
        "name" : "Green",
        "hex" : "00ff00"
    },
    "position" : {
        "_id" : "",
        "name" : "Defence",
        "type" : "position"
    },
    "ageGroup" : {
        "_id" : "",
        "name" : "Minor Peewee",
        "type" : "age"
    },
    "companyId" : ""
}

我目前正在使用Mongo的聚合来按ageGroup.name对文档进行分组,返回:

//Query
Jerseys.aggregate([
  {$match: { companyId: { $in: companyId } } },
  {$group: {_id: "$ageGroup.name", jerseys: { $push: "$$ROOT" }} }
]);

//returns
{
   _id: "Minor Peewee",
   jerseys: array[]
}

但我希望它也按年龄组中的position.name分组.即:

{
  _id: "Minor Peewee",
  positions: array[]
}
//in positions array...
{
  _id: "Defence",
  jerseys: array[]
}
// or ageGroups->positions->jerseys if that makes more sense.

我尝试了多个组,但我认为我没有正确设置它我似乎总是得到一个_id的数组.我正在使用Meteor作为服务器,而我正在使用流星方法.

Answer 1

您可以_id在第一个分组阶段使用复合聚合.

然后,您可以将其中一个键用作_id最终聚合的"主" ,将$push另一个键用作另一个数组.

Jerseys.aggregate([
  {
    $match: { companyId: { $in: companyId } } 
  },
  { 
    $group: { // each position and age group have an array of jerseys
      _id:   { position: "$position", ageGroup: "$ageGroup" }, 
      jerseys: { $push: "$$ROOT" } 
    } 
  }, 
  { 
    $group: { // for each age group, create an array of positions
      _id: { ageGroup: "$_id.ageGroup" }, 
      positions: { $push: { position: "$_id.position", jerseys:"$jerseys" } } 
    } 
  } 
]);