MongoDB:如何更新由数组中的索引引用的数组中的单个子元素? [英] MongoDB: How do I update a single subelement in an array, referenced by the index within the array?

问题描述

我正在尝试更新 mongodb 文档中包含在数组中的单个子元素.我想使用它的数组索引引用该字段(数组中的元素没有任何我可以保证将是唯一标识符的字段).看起来这应该很容易做到，但我无法弄清楚语法.

I'm trying to update a single subelement contained within an array in a mongodb document. I want to reference the field using its array index (elements within the array don't have any fields that I can guarantee will be unique identifiers). Seems like this should be easy to do, but I can't figure out the syntax.

这是我想在伪 json 中做的事情.

Here's what I want to do in pseudo-json.

之前:

{
  _id : ...,
  other_stuff ... ,
  my_array : [
    { ... old content A ... },
    { ... old content B ... },
    { ... old content C ... }
  ]
}

之后:

{
  _id : ...,
  other_stuff ... ,
  my_array : [
    { ... old content A ... },
    { ... NEW content B ... },
    { ... old content C ... }
  ]
}

看起来查询应该是这样的:

Seems like the query should be something like this:

//pseudocode
db.my_collection.update(
  {_id: ObjectId(document_id), my_array.1 : 1 },
  {my_array.$.content: NEW content B }
)

但这行不通.我花了很长时间搜索 mongodb 文档，并尝试了这种语法的不同变体(例如，使用 $slice 等).我找不到有关如何在 MongoDB 中完成此类更新的任何明确说明.

But this doesn't work. I've spent way too long searching the mongodb docs, and trying different variations on this syntax (e.g. using $slice, etc.). I can't find any clear explanation of how to accomplish this kind of update in MongoDB.

推荐答案

正如预期的那样，一旦您知道如何进行，查询就会很容易.这是python中的语法:

As expected, the query is easy once you know how. Here's the syntax, in python:

db["my_collection"].update(
    { "_id": ObjectId(document_id) },
    { "$set": { 'documents.'+str(doc_index)+'.content' : new_content_B}}
)

这篇关于MongoDB:如何更新由数组中的索引引用的数组中的单个子元素?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！