$ setIntersection是否可以与对象一起使用?

问题描述

我似乎无法获得$ setIntersection来处理对象.

I cant seem to get $setIntersection to work with objects.

示例:

对象1:

[
  {name: "test5", value:5},
  {name: "test4", value:4},
  {name: "test3", value:3},
  {name: "test2", value:2}
]

对象2:

[
  {name: "test5", value:5},
  {name: "test422", value:422},
  {name: "test333", value:3333},
  {name: "test211", value:211}
]

$ setIntersection将返回我[]而不是:

$setIntersection would return me [] instead of this:

[
  {name: "test5', value:5}
]

如果$ setIntersection无法与Objects一起使用，是否可以使用其他解决方法?

If $setIntersection does not work with Objects, is there any work around that I can use?

推荐答案

似乎您做错了:

如果我插入一个具有如下数组的对象:

If I insert an object with an array like so:

db.test.insert({
    "a" : [
        {
            "name" : "test5",
            "value" : 5.0
        },
        {
            "name" : "test4",
            "value" : 4.0
        },
        {
            "name" : "test3",
            "value" : 3.0
        },
        {
            "name" : "test2",
            "value" : 2.0
        }
    ]
})

然后我使用 $ setInsersection 以及所提供的对象数组，如下所示:

And I run an .aggregate() with $setInsersection and the supplied array of objects like so:

db.getCollection('test').aggregate([
  { "$project": {
    "a": {
      "$setIntersection": [
        "$a",
        [
          {name: "test5", value: 5},
          {name: "test422", value: 422},
          {name: "test333", value: 3333},
          {name: "test211", value: 211}
        ]
      ]
    }
  }}
])

然后我得到了预期的结果:

Then I get the expected result:

/* 1 */
{
    "_id" : ObjectId("59f02df75b9b8bb266a563cb"),
    "a" : [
        {
            "name" : "test5",
            "value" : 5.0
        }
    ]
}

如果属性是反向的"，例如:

If the properties are "reversed", as in:

db.getCollection('test').aggregate([
  { "$project": {
    "a": {
      "$setIntersection": [
        "$a",
        [
          { value: 5, name: "test5" },
          {name: "test422", value: 422},
          {name: "test333", value: 3333},
          {name: "test211", value: 211}
        ]
      ]
    }
  }}
])

然后结果数组为"empty"，这应该是预期的，因为 {"name":"test5"，"value":5} 与 {"value:5，" test:名称} 涉及到集合".

Then the result array is "empty", as should be expected because { "name": "test5", "value": 5 } is not the same as { "value": 5, "test": name } as far as a "set" is concerned.

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