在同一文档MongoDB中将元素从一个数组移动到另一个数组 [英] Move an element from one array to another within same document MongoDB

问题描述

我有如下数据:

{
  "_id": ObjectId("4d525ab2924f0000000022ad"),
  "array": [
    { id: 1, other: 23 },
    { id: 2, other: 21 },
    { id: 0, other: 235 },
    { id: 3, other: 765 }
  ],
  "zeroes": []
}

我想从一个数组中拉出一个元素，然后将其$ push到同一文档中的第二个数组中，以产生类似于以下内容的东西:

I'm would like to to $pull an element from one array and $push it to a second array within the same document to result in something that looks like this:

{
  "_id": ObjectId("id"), 
  "array": [
    { id: 1, other: 23 },
    { id: 2, other: 21 },
    { id: 3, other: 765 }
  ],
  "zeroes": [
    { id: 0, other: 235 }
  ]
}

我意识到我可以通过先查找然后进行更新来做到这一点，

I realize that I can do this by doing a find and then an update, i.e.

db.foo.findOne({"_id": param._id})
.then((doc)=>{
  db.foo.update(
    {
      "_id": param._id
    },
    {
      "$pull": {"array": {id: 0}},
      "$push": {"zeroes": {doc.array[2]} }
    }
  )
})

我想知道是否可以使用原子功能. 像

I was wondering if there's an atomic function that I can do this with. Something like,

db.foo.update({"_id": param._id}, {"$move": [{"array": {id: 0}}, {"zeroes": 1}]}

发现这篇文章慷慨地提供了我使用的数据，但问题在4年后仍未解决.在过去的四年中，是否为此制定了解决方案?

Found this post that generously provided the data I used, but the question remains unsolved after 4 years. Has a solution to this been crafted in the past 4 years?

将元素从$ pull移至另一个数组

推荐答案

没有在MongoDB中.话虽如此，最简单的解决方案是两阶段方法:

There is no $move in MongoDB. That being said, the easiest solution is a 2 phase approach:

1. 查询文档
2. 使用 $pull 和 $push /这里的重要部分是确保所有内容都是幂等的，它是将原始数组文档包含在更新查询中.

   The important part here, to make sure everything is idempotent, is to include the original array document in the query for the update.

   提供以下格式的文件:

   {
       _id: "foo",
       arrayField: [
           {
               a: 1,
               b: 1
           },
           {
               a: 2,
               b: 1
           }
       ]
   }
   

   让我们说您想将{ a: 1, b: 1 }移到另一个字段(可能称为someOtherArrayField)，您想要做类似的事情.

   Lets say you want to move { a: 1, b: 1 } to a different field, maybe called someOtherArrayField, you would want to do something like.

   var doc = db.col.findOne({_id: "foo"});
   var arrayDocToMove = doc.arrayField[0];
   db.col.update({_id: "foo", arrayField: { $elemMatch: arrayDocToMove} }, { $pull: { arrayField: arrayDocToMove }, $addToSet: { someOtherArrayField: arrayDocToMove } })
   

   我们使用 $elemMatch 的原因是确保自我们首次查询文档以来，要从数组中删除的字段没有更改.当与 $pull 结合使用时，它也不是严格的必要，但在这种情况下，我通常会过分谨慎.如果您的应用程序中没有并行性，而您只有一个应用程序实例，那么就没有严格的必要.

   The reason we use the $elemMatch is to be sure the field we are about to remove from the array hasn't changed since we first queried the document. When coupled with a $pull it also isn't strictly necessary, but I am typically overly cautious in these situations. If there is no parallelism in your application, and you only have one application instance, it isn't strictly necessary.

   现在，当我们检查生成的文档时，我们得到:

   Now when we check the resulting document, we get:

   db.col.findOne()
   {
           "_id" : "foo",
           "arrayField" : [
                   {
                           "a" : 2,
                           "b" : 1
                   }
           ],
           "someOtherArrayField" : [
                   {
                           "a" : 1,
                           "b" : 1
                   }
           ]
   }
   

   这篇关于在同一文档MongoDB中将元素从一个数组移动到另一个数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！