Update subarray of objects in mongodb

Question

I have this document in my database:

{
    "_id": "ObjectId(...)",
    "chapters": [
        {
            "_id": "ObjectId(...)",
            "link": "128371.html",
            "content": ""
        }
    ]
}

The chapters array can have up to 3k items, and I have to populate each content attribute with some info. I want to be able to save the info I want inside the right object. Until now I was able to change the content attribute generally (in all items), but I am having trouble filtering it. This is what I managed to code using what I found in other questions:

let content = "Testing";
await models.ListNovel.updateOne(
  { link: novel_link },
  { $set: { "chapters.$[].content": content } }
);

I saw that { arrayFilters: [{ link: { $eq: chapter_link } }], multi: false } may work in some cases, but I don't use the link identifier in the update.

Thank you!

UPDATE

Similar to Suleyman's solution, I ended up with the following working code, I hope it may be useful for you.

await models.ListNovel.updateOne(
  { link: novel.link },
  { $set: { "chapters.$[elem].content": content } },
  {
    multi: true,
    arrayFilters: [{ "elem.link": { $eq: chapter.link } }]
  }
);

SuleymanSah · Accepted Answer · 2020-02-16 18:43:19Z

The condition in updateOne must match parent object, but you are using { link: novel_link } which belongs to the inner array object field, so it cannot find the document, and update doesn't happen.

To illustrate this, let's say your schema is like this:

const mongoose = require("mongoose");

const schema = new mongoose.Schema({
  name: String,
  chapters: [
    new mongoose.Schema({
      link: String,
      content: String
    })
  ]
});

module.exports = mongoose.model("ListNovel", schema);

Let's have this existing document in this collection:

{
    "_id": "5e498a1fe21eea0e10690e39",
    "name": "Novel1",
    "chapters": [
        {
            "_id": "5e498a1fe21eea0e10690e3b",
            "link": "128371.html",
            "content": ""
        },
        {
            "_id": "5e498a1fe21eea0e10690e3a",
            "link": "222222.html",
            "content": ""
        }
    ],
    "__v": 0
}

If we want to update this document's chapter with "link": "128371.html", first we need to find it with name or _id field, and update it using the filtered positional operator $.

router.put("/novels/:name", async (req, res) => {
  const novel_link = "128371.html";
  const content = "Testing";

  const result = await ListNovel.findOneAndUpdate(
    { name: req.params.name },
    {
      $set: { "chapters.$[chapter].content": content }
    },
    {
      arrayFilters: [{ "chapter.link": novel_link }],
      new: true
    }
  );
  res.send(result);
});

Here I used findOneAndUpdate to immediately retrieve the updated document, but you can also use the updateOne instead of findOneAndUpdate.

The result will be like this:

{
    "_id": "5e498a1fe21eea0e10690e39",
    "name": "Novel1",
    "chapters": [
        {
            "_id": "5e498a1fe21eea0e10690e3b",
            "link": "128371.html",
            "content": "Testing"  // => UPDATED
        },
        {
            "_id": "5e498a1fe21eea0e10690e3a",
            "link": "222222.html",
            "content": ""
        }
    ],
    "__v": 0
}

Great explanation, Suleyman! After some time going through the documentation, I ended up with a pretty similar solution, using updateOne and the $eq operator.

Collectives™ on Stack Overflow

Update subarray of objects in mongodb

UPDATE

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

UPDATE

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related