Django 为什么此聚合查询在MongoDB中从命令行工作，而不是通过MongoEngine工作？

我有一个查询，当它直接在MongoDB中执行时，它会按预期运行，但我在试图通过MongoEngine使其工作时遇到了一些麻烦

开发环境

MongoDB 3.0.7

Mongoengine 0.10

Pymongo 3.1

Django 1.8.4

原始查询

当从命令行执行此查询时，它在MongoDB中执行得非常好，可以检索大量结果

db.collection.aggregate([{$project: {
         "variant":1,
         "version":1,
         "date":1,
           "quarter":{$cond:[{$lte:[{$month:"$date"},3]},
                        "Q1",
                        {$cond:[{$lte:[{$month:"$date"},6]},
                                "Q2",
                                {$cond:[{$lte:[{$month:"$date"},9]},
                                        "Q3",
                                        "Q4"]}]}]}}},{$group:{"_id":{"quarter":"$quarter", "year":{$year:"$date"}},
  "total":{$sum:1},
  "details":{$push:{
     variant:"$variant",
     version:"$version",
     date:"$date" }}}}])

MONGOENGINE查询

这是我在MongoEngine中的尝试。 它抛出“管道元素1不是对象”错误

---

我做错了什么？

我只需要删除括号并将逗号分隔的参数传递给聚合方法

project = {"$project": {
        "variant":1,
        "version":1,
        "date":1,
        "quarter":{"$cond":[{"$lte":[{"$month":"$date"},3]},
                    "Q1",
                    {"$cond":[{"$lte":[{"$month":"$date"},6]},
                          "Q2",
                          {"$cond":[{"$lte":[{"$month":"$date"},9]},
                                "Q3",
                                "Q4"]}]}]}}}
group = {"$group":{"_id":{"quarter":"$quarter", "year":{"$year":"$date"}},
     "total":{"$sum":1},
     "details":{"$push":{
        "variant":"$variant",
        "version":"$version",
        "date":"$date" }}}}

queryset = Collection.objects.aggregate( project, group )

project = {"$project": {
        "variant":1,
        "version":1,
        "date":1,
        "quarter":{"$cond":[{"$lte":[{"$month":"$date"},3]},
                    "Q1",
                    {"$cond":[{"$lte":[{"$month":"$date"},6]},
                          "Q2",
                          {"$cond":[{"$lte":[{"$month":"$date"},9]},
                                "Q3",
                                "Q4"]}]}]}}}
group = {"$group":{"_id":{"quarter":"$quarter", "year":{"$year":"$date"}},
     "total":{"$sum":1},
     "details":{"$push":{
        "variant":"$variant",
        "version":"$version",
        "date":"$date" }}}}

queryset = Collection.objects.aggregate( project, group )