Mongodb 基于条件查找和计数mongo数组中的一致性

假设我有一个文档集，类似于：

{
_id :ObjectId("45645645gdfgdfgdf"),
article:"article one",
topic:["config","develop","show"],
keys[
    {subject:"one",object"abc"},
    {subject:"one",object"def"},
    {subject:"two",object"ghi"},
    {subject:"four",object"jkl"},
    {subject:"four",object"mnl"},
    {subject:"four",object"mnl"},
]
},
{
_id :ObjectId("45645645gdfgdfgdf"),
article:"article two",
topic:["config","installing"],
keys[
    {subject:"one",object"abc"},
    {subject:"one",object"def"},
    {subject:"two",object"ghi"},
    {subject:"two",object"jkl"},
]
},
{
_id :ObjectId("45645645gdfgdfgdf"),
article:"article three",
topic:["config","installing"],
keys[
    {subject:"five",object"abc"},
    {subject:"five",object"def"},
    {subject:"two",object"ghi"},
    {subject:"two",object"jkl"},
]
}

我想根据一个条件计算数组中的每个主题，并按主题过滤，例如，假设我按主题搜索：“config”和主题：[“one”，“four”]结果需要

{article :"article one", sum:5},{article :"article two", sum:2}

---

thks提前

您可以使用下面的聚合

db.colname.aggregate([
  {"$match":{"topic":"config","subject":{"$in":["one","four"]}}},
  {"$project":{
    "article":1,
    "sum":{
      "$size":{
        "$filter":{
          "input":"$keys",
          "cond":{"$in":["$$this.subject",["one","four"]]}
        }
      }
    }
  }}
])

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谢谢，这段代码帮助我理解了mongo的查询思想