Upsert in nested array doesn't create parent document

Question

Schema

{
    chapter: {
        required: true,
        type: Schema.Types.ObjectId,
        ref: "Chapter",
    },
    questions: {
        type: [Number]
    },
};

Here is an example document

{
   "_id":{
      "$oid":"5ff4b728b6af610f0851d2a6"
   },
   "chapters":[
      {
         "chapter":{
            "$oid":"611478ab34dde61f28dbe4d3"
         },
         "questions":[
            35,
            29,
            167,
            180,
            101,
            16,
            71,
            23
         ]
      },
      {
         "chapter":{
            "$oid":"611478ac34dde61f28dbe4d8"
         },
         "questions":[
            162
         ]
      }
   ]
}

I want to "$addToSet" on "questions", such as

const someId = SOME_ID;
const chapterId = "611478ac34dde61f28dbe4d8";
const update = {
    $addToSet: {
        "chapters.$.questions": {
            $each: [5, 10, 32, 6],
        },
    },
};
await model.findOneAndUpdate(
    {
        _id: someId,
        "chapters.chapter": chapterId,
    },
    update,
    { upsert: true }
)
    .lean()
    .exec();

This works. However, if there is no document, the "upsert" doesn't create the document. How can I rewrite the operation so that it can update (addToSet) as well as ensure the document is created if it didn't exist?

mohammad Naimi · Accepted Answer · 2021-08-25 16:52:40Z

1

I checked MongoDB native query use these

db.con.collection('example').updateOne(
    {"chapters": {$elemMatch:{"chapter.id":ObjectId("611478ac34dde61f28dbe4d8")}}},
    {$addToSet: {
        "chapters.$.questions": {
            $each: [5, 10, 32, 6],
        },
    }},
    {upsert: true})

you should find the element of array using elemMatch

{"chapters": {$elemMatch:{"chapter.id":"611478ac34dde61f28dbe4d8"}}}

edited Aug 25, 2021 at 16:52

answered Aug 25, 2021 at 3:11

mohammad Naimi

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8 Comments

Chique Over a year ago

Unfortunately, it doesn't work when there is no document. It returns "BadValue" error.

mohammad Naimi Over a year ago

is chapter object in chapters array , or chapters array is your collection ?

Chique Over a year ago

You can see the example document structure I have in the question. Chapter object is in chapters array.

mohammad Naimi Over a year ago

ok my query is mongo query not mongoose did you translate my query to mongoose?

mohammad Naimi Over a year ago

did you use {$elemMatch:{"chapter.id":ObjectId("611478ac34dde61f28dbe4d8")}} ?

|

Chique · Accepted Answer · 2021-08-25 14:26:59Z

I figured out, for some reason, I can't $addToSet if the parent object is not present. So I had to make one more operation.

Inspired from this Stackoverflow answer.

I fetch the "chapters" which I need to add.
From this list of fetched chapters, I check which ones exist and which ones don't.
Using the knowledge from point 2, I am using $push to add the chapters which didn't exist entirely, and "adding to set ($addToSet)" questions on the chapters which do exist.

I am posting the code which works for me.

//Data to add (which chapter?: questionNumber[])
const docId = "SOMEID";
const questionsToAdd = {
    "611478ab34dde61f28dbe4d3": [1,5,6,10],
    "611478ab34dde61f28dbe4d8": [5,8,20,30],
};

//Find the chapters from questionsToAdd which exist
const existingDoc = await model.findOne({
    _id: docId,
    chapters: { $elemMatch: { chapter: { $in: Object.keys(questionsToAdd) } } },
})
    .select(["chapters.chapter"])
    .lean()
    .exec();

// Objectify the array of chapters
const existingChapters = (existingDoc?.chapters ?? []).map((x) => "" + x.chapter);

// Prepare what to insert, what to update
const updateObject = {
    $addToSet: {},
    arrayFilters: [],
    $push: [],
};
for (const [index, [chapterId, questionIndices]] of Object.entries(questionsToAdd).entries()) {
    if (existingChapters.includes(chapterId)) {
        updateObject.$addToSet["chapters.$[filter" + index + "].questions"] = { $each: questionIndices };
        updateObject.arrayFilters.push({
            ["filter" + index + ".chapter"]: Types.ObjectId(chapterId),
        });
    } else {
        updateObject.$push.push({
            chapter: chapterId,
            questions: questionIndices,
        });
    }
}

if (updateObject.arrayFilters.length) {
    // *Add to set the chapters which exist
    await model.findOneAndUpdate(
        { _id: userId },
        {
            $addToSet: updateObject.$addToSet,
        },
        {
            arrayFilters: updateObject.arrayFilters,
            upsert: true,
        }
    )
        .lean()
        .exec();
}

if (updateObject.$push.length) {
    // *Push the ones that does not exist
    await model.findOneAndUpdate(
        { _id: userId },
        {
            $push: { chapters: updateObject.$push },
        },
        {
            upsert: true,
        }
    )
        .lean()
        .exec();
}

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