用管道（聚合或更新）以特定索引将项目推入数组-MongoDB

发布于 2025-02-13 18:42:46 字数 1001 浏览 0 评论 0 原文

受，我寻找了一种常见的做法，可以将项目插入管道内的特定索引中的数组，然后找不到一个。假设我的文档看起来像：

[
  {
    _id: ObjectId("62c2e94e65f32725f8f62b79"),
    updatedAt: ISODate("2022-06-29T13:10:36.659Z"),
    createdAt: ISODate("2022-06-29T08:06:51.264Z"),
    userID: 1,
    myImage: "imageC",
    images: [
      "imageA",
      "imageB",
      "imageD",
      "imageE",
      "imageF"
    ]
  }
]

我想将值插入字段 myimage images array，specificaly in Index 2中，所以预期的结果是一个更新的文档：

[
  {
    _id: ObjectId("62c2e94e65f32725f8f62b79"),
    updatedAt: ISODate("2022-06-29T13:10:36.659Z"),
    createdAt: ISODate("2022-06-29T08:06:51.264Z"),
    userID: 1,
    myImage: "imageC",
    images: [
      "imageA",
      "imageB",
      "imageC",
      "imageD",
      "imageE",
      "imageF"
    ]
  }
]

原文

inspired by another question, I looked for a common practice for inserting an item into an array at a specific index inside a pipeline, and could not find one.
Assuming my document looks like:

[
  {
    _id: ObjectId("62c2e94e65f32725f8f62b79"),
    updatedAt: ISODate("2022-06-29T13:10:36.659Z"),
    createdAt: ISODate("2022-06-29T08:06:51.264Z"),
    userID: 1,
    myImage: "imageC",
    images: [
      "imageA",
      "imageB",
      "imageD",
      "imageE",
      "imageF"
    ]
  }
]

And I want to insert the value in field myImage to images array, specificaly at index 2, so the expected result is an updated document:

[
  {
    _id: ObjectId("62c2e94e65f32725f8f62b79"),
    updatedAt: ISODate("2022-06-29T13:10:36.659Z"),
    createdAt: ISODate("2022-06-29T08:06:51.264Z"),
    userID: 1,
    myImage: "imageC",
    images: [
      "imageA",
      "imageB",
      "imageC",
      "imageD",
      "imageE",
      "imageF"
    ]
  }
]

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怕倦 2025-02-20 18:42:46

这可以使用聚合管道或管道更新来完成。在这种情况下，简单的选项是更新管道。

这里的想法是在 $$ value $ size 中使用 $降低步骤以找到正确的位置将项目插入到：

db.collection.update(
{userID: 1},
[
  {$set: {
      images: {
        $reduce: {
          input: "$images",
          initialValue: [],
          in: {$concatArrays: [
              "$value",
              {$cond: [
                  {$eq: [{$size: "$value"}, index]},
                  ["$myImage", "$this"],
                  ["$this"]
                ]
              }
            ]
          }
        }
      }
    }
  }
])

查看其在

This can be done using an aggregation pipeline or an update with pipeline. In this case the simple option is an update pipeline.

The idea here is to use the $size of the $$value in the $reduce step to find the right place to insert the item into:

db.collection.update(
{userID: 1},
[
  {$set: {
      images: {
        $reduce: {
          input: "$images",
          initialValue: [],
          in: {$concatArrays: [
              "$value",
              {$cond: [
                  {$eq: [{$size: "$value"}, index]},
                  ["$myImage", "$this"],
                  ["$this"]
                ]
              }
            ]
          }
        }
      }
    }
  }
])

See how it works on the playground example

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