An update in the array of objects inside another array of objects.
mongodb field that I'm working on:
otherFields: values,
tasks: [
{
_id: mongodb.objectID(),
title: string,
items:[{
_id: mongodb.objectID(),
title: string,
completed: boolean //field need to be update.
}]
},
{}...
],
otherFields: value
sample mongodb document
I need to find the document using the task_id and the item_id and update a completed field in item of a task. Using the mongoose findOneAndUpdate method
const path = "tasks.$.items." + item_id + "completed";
collectionName.findOneAndUpdate(
{ _id: req.user._id, "tasks._id": taskID },
{ $set: { [path]: true }});
The above query doesn't work!!!
There is no need to use multiple query conditions, since you'd like to update a specific item that has an unique ID. Therefore you could use something along the lines:
collectionName.findOneAndUpdate(
{ 'tasks.items._id': itemID },
...
);
Keep in mind this structure is far away from optimized as it would basically look through the entire database...
Also now that I think of it, you'd also have issue with the update, as there are two nested arrays within the document. Read more here: How to Update Multiple Array Elements in mongodb
Related
I have an Array of objects in mongoDB as follow
Initially there is only the heartRate field inside the object. Now I want to add new fields to this object along with the existing heartRate field.
Also there can be multiple objects inside the dailyReadings array. Therefore, I need to add new fields only to the last object using nodejs and expressjs
I tried using the $push method but ended up adding new object intead of adding the fields to the last object. Is there a way to achieve this? Thanks in advance!
Why I am doing this (For further understanding):-
I have developed a mobile app to read the heart rate. Initially it will save the heart rate in the database as a new object (As in the image). Then, there are several other data sent through a desktop application which needs to add to the same object (Which is the last object in the dailyReadings array)
There is no straight way to do this, you can try update with aggregation pipeline starting from MongoDB 4.2,
$size to get total elements in dailyReadings array
$subtract to minus 1 from above total elements
$slice to get elements other than the last object element
$slice to get last object element by -1 from dailyReadings
$arrayElemAt to select first object element from array
$mergeObjects to merge existing object fields of the last object and new fields that you want to insert
$concatArrays to concat first slice array and second updated object
db.collection.update(
{}, // put your query condition
[{
$set: {
dailyReadings: {
$concatArrays: [
{
$slice: [
"$dailyReadings",
0,
{ $subtract: [{ $size: "$dailyReadings" }, 1] }
]
},
[
{
$mergeObjects: [
{ $arrayElemAt: [{ $slice: ["$dailyReadings", -1] }, 0] },
{
newField: "1"
}
]
}
]
]
}
}
}]
)
Playground
In order for you to add fields to the last object, the heartRate should be an object with a schema containing the following
Array (for you to add to)
any other necessary data type you'd want the object to have
you must define a complex schema using mongoose, perform the following changes to your file of model
const mongoose = require('mongoose');
const childSchema = mongoose.Schema({
heartRate: {type: Array, required: true}
array: {type: Array, required: false}, //change the required parameter based on your requirement
});
const parentSchema = mongoose.Schema({
dailyReadings: {
type: childSchema,
required: false //change the required parameter based on your requirement
},
});
module.exports = mongoose.model('modelCollection', parentSchema);
So basically you need to define the child schema, and change the type of dailyReadings to that schema and add to the array of different objects.
I have a MongoDB collection called users with documents that look like:
{
_id: ObjectId('123'),
username: "abc",
avatar: "avatar/long-unique-random-string.jpg",
connections: [ObjectId('abc'), ObjectId('xyz'), ObjectId('lmn'), ObjectId('efg')]
}
This document belongs to the users collection.
What I want to do:
First, find one document from the users' collection that matches _id -> '123'.
Project the connections field received from step 1, which is an array of ObjectIds of other users within the same collection.
Find all documents of users from the array field projected in step 2.
Project and return an array of only the username and avatar of all those users from step 3.
While I know that I can do this in two separate queries. First using findOne which returns the friends array. Then, using find with the results of findOne to get all the corresponding usernames and avatars.
But, I would like to do this in one single query, using the aggregation pipeline.
What I want to know, is it even possible to do this in one query using aggregation?
If so, what would the query look like?
What, I currently have:
await usersCollection
.aggregate([
{ $match: { _id: new ObjectId(userId) } },
{ $project: { ids: "$connections" } },
{ $match: { _id: { $in: "ids" } } },
{
$project: {
username: "$username",
avatar: { $ifNull: ["$avatar", "$$REMOVE"] },
},
},
])
.toArray()
I know this is wrong because each aggregation stage receives the results from the previous stage. So, the second match cannot query on the entire users' collection, as far as I know.
I'm using MongoDB drivers for nodeJS. And I would like to avoid $lookup for possible solutions.
query to find all the elements in the array in mongoose dynamically
below is the object
var res1= {
"category":["travel","cafe"],
"amount":"300"
}
There could be more elements in the category but I want to create the query which automatically finds all the elements in the database just like forEach works
The $in operator should to the trick. $in will look for documents where the provided field matches any of the values in the array. the query would look like this:
Detail.find({
category: { $in: ["travel", "cafe"] },
amount: 300
})
assuming the filters are coming in dynamically on the request, and that req.body.categories is an array of desired categories:
Detail.find({
category: { $in: req.body.categories },
amount: req.body.amount
})
I have a Schema:
var ProjectSchema = new Schema({
name: {
type: String,
default: ''
},
topics: [{
type: Schema.ObjectId,
ref: 'Topic'
}],
user: {
type: Schema.ObjectId,
ref: 'User'
}
});
What I want to do is get an array with all topics from all projects. I cannot query Topic directly and get a full list because some topics are unassigned and they do not hold a reference back to a Project (for reasons of avoiding two way references). So I need to query Project and aggregate some how. I am doing something like:
Project.aggregate([{$project:{topics:1}}]);
But this is giving me an array of Project objects with the topics field. What I want is an array with topic objects.
How can I do this?
When dealing with arrays you typically want to use $unwind on the array members first and then $group to find the distinct entries:
Project.aggregate(
[
{ "$unwind": "$topics" },
{ "$group": { "_id": "$topics._id" } }
],
function(err,docs) {
}
)
But for this case, it is probably simplier to just use .distinct() which will do the same as above, but with just an array of results rather than documents:
Project.distinct("topics._id",function(err,topics) {
});
But wait there a minute because I know what you are really asking here. It's not the _id values you want but your Topic data has a property on it like "name".
Since your items are "referenced" and in another collection, you cannot do an aggregation pipeline or .distinct() operation on the property of a document in another collection. Put basically "MongoDB does not perform Joins" and mongoose .populate() is not a join, just something that "emulates" that with additional query(ies).
But you can of course just find the "distinct" values from "Project" and then fetch the information from "Topic". As in:
Project.distinct("topics._id",function(err,topics) {
Topic.find({ "_id": { "$in": topics } },function(err,topics) {
});
});
Which is handy because the .distinct() function already returned an array suitable for use with $in.
I have a schema defined in mongoose as follow:
var VolunteerSchema = new Schema ({
......
other fields
.....
preferLocations:[{
type: Schema.ObjectId,
ref: 'Location'
}]
.....
});
I am using volunteer.save() method to update the model.
While updating to volunteer model i get the error as follow:
{ [DivergentArrayError: For your own good, using `document.save()` to update an
array which was selected using an $elemMatch projection OR populated using skip,
limit, query conditions, or exclusion of the _id field when the operation resul
ts in a $pop or $set of the entire array is not supported. The following path(s)
would have been modified unsafely:
preferLocations
Use Model.update() to update these arrays instead.]
message: 'For your own good, using `document.save()` to update an array which
was selected using an $elemMatch projection OR populated using skip, limit, quer
y conditions, or exclusion of the _id field when the operation results in a $pop
or $set of the entire array is not supported. The following path(s) would have
been modified unsafely:\n preferLocations\nUse Model.update() to update these a
rrays instead.',
name: 'DivergentArrayError' }
While updating the location I collect the _ids field in array and asigned to preferLocations as given below:
volunteer.preferLocations = locationIdsArray;
I don't get the error when I remove this line.What am I doing wrong?
When using $elemMatch in a projection, do not use document.save(). Instead, manually update your document using Model.update(). In your case you should try
volunteer.findOneAndUpdate(
{
_id: ObjectId("567452bae5b25d6e6c1a0f7e"),
localization: { '$elemMatch': { language: 'de' } }
},
{
$set: { 'localization.$.name' : "Neuer Name" }
}).exec(//...
});
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