如果在单个查询中 $pull 后数组计数为零，则 mongodb 删除文档 [英] mongodb remove document if array count zero after $pull in a single query

问题描述

我有一个要求，其中我的 comments 架构如下所示

I have a requirement where my comments schema looks like the following

{
  "_id": 1,
  "comments": [
    { "userId": "123", "comment": "nice" },
    { "userId": "124", "comment": "super"}
  ]
}

我想根据 userId 字段提取元素.我正在做以下查询

I would like to pull the elements based on the userId field. I am doing the following query

comments.update({},{$pull:{comments:{userId:"123"}}})

我的要求是，如果在 pull 运算符之后数组长度变为零，我需要出于某种原因删除整个文档.是否可以在单个查询中执行此操作?

My requirement is that if the array length became zero after the pull operator I need to remove the entire document for some reason.Is there a away to do this in a single query?

PS:我使用的是 mongodb 驱动程序.不是猫鼬

PS:I am using the mongodb driver.Not the mongoose

推荐答案

如果我没看错你的问题，在 $pull 之后，如果 comments 数组是空(零长度)，然后删除文档({ _id: '', comments: [] }).

If I'm reading your question right, after the $pull, if the comments array is empty (zero length), then remove the document ({ _id: '', comments: [] }).

这应该删除 comments 数组存在且为空的所有文档:

This should remove all documents where the comments array exists and is empty:

comments.remove({ comments: { $exists: true, $size: 0 } })

我有一个类似的要求并使用了这个(虽然使用了mongoose):

I had a similar requirement and used this (using mongoose though):

await Attributes.update({}, { $pull: { values: { id: { $in: valueIds } } } }, { multi: true })
await Attributes.remove({ values: { $exists: true, $size: 0 } })

不确定是否可以在一次操作中完成此操作.

Not sure if it's possible to do this in one operation or not.

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