monset聚合查询中的$ unwind和$ match后，$ set不替换值

Question

我正在尝试查找和更新嵌套对象数组中的某些字段。我正在用$unwind展平数组，然后使用$match隔离要更新的实例，但是$set似乎不起作用。也许我不能以这种方式使用它？

尝试$set之前的两个条目：

[
   {
     _id: 5dabcdf7501b3b4ab66f9f76,
     tasks: {
       _id: 5dabcde5c4a0ab4aa106af7d,
       task: '19',
       name: 'beyond',
       dimension: 'Transformational Leadership',
       subDimension: 'unknown',
       points: 1,
       imgUrl: 'imgs/19.svg',
       text: 'You completed a custom challenge!',
       userId: '5dabcdf7501b3b4ab66f9f76',
       createdAt: '48-Mo:01:48'
     },
     awards: [],
     firstName: 'bob',
     lastName: 'bob',
     location: 'Campbell, USA',
     unit: 'AMSBG',
     group: 3,
     team: 1,
     createdAt: 2019-10-20T03:01:11.071Z,
     updatedAt: 2019-10-29T16:03:54.002Z,
     no_of_tasks: 9,
     points: 9
   },
   {
     _id: 5dabcdf7501b3b4ab66f9f7d,
     tasks: {
       _id: 5dabcde5c4a0ab4aa106af7d,
       task: '19',
       name: 'beyond',
       dimension: 'Transformational Leadership',
       subDimension: 'unknown',
       points: 1,
       imgUrl: 'imgs/19.svg',
       text: 'You completed a custom challenge!',
       userId: '5dabcdf7501b3b4ab66f9f7d',
       createdAt: '48-Mo:01:48'
     },
     awards: [],
     firstName: 'bobette',
     lastName: 'bob',
     location: 'Taiperi',
     unit: 'Finance',
     group: 1,
     team: 1,
     createdAt: 2019-10-20T03:01:11.072Z,
     updatedAt: 2019-10-29T18:24:20.480Z,
     no_of_tasks: 40,
     points: 40
   }
 ]

我认为应该工作的查询：

const tasks = await User.aggregate([
        { $unwind: '$tasks' },
        { $match: {'tasks.name': foo.name} },
        { $set:
          {'tasks.text': foo.text,
          'tasks.subDimension': foo.subDimension }
        }
    ])

希望了解为什么它会失败