I have a mongoose schema like this:
A = {
_id: Schema.Types.ObjectId,
arrayA:[{
_id,
nestedArray: [Schema.Types.ObjectId]
}],
arrayB: [Schema.Types.ObjectId]
}
I would like to push an Object Id into nestedArray in specific arrayA object AND
arrayB should contains an specific Object Id by following code:
A.update({'arrayA._id': arrayAId, arrayB: {$in: [arrayContainsSomeArrayBIds]}},
{$push: {'arrayA.$.nestedArray': nestedArrayId}}, function(err) {
});
However, the Object Id is pushed into nestedArray of the last object in arrayA.
If arrayB: {$in: [arrayContainsSomeArrayBIds]} is removed, the Object Id can be pushed into correct object in arrayA.
mongoose version: 3.8.21
Can anyone help me to find out the problem?
Currently it is not possible in MongoDB to update an a array element with the positional operator, when the query document contains references to other arrays apart from the one being updated.
The below code, contains reference to two arrays fields: arrayA and arrayB, when
the update is issued on arrayA. This is invalid and would lead to undesired behavior.
A.update({'arrayA._id': arrayAId, arrayB: {$in: [arrayContainsSomeArrayBIds]}},
{$push: {'arrayA.$.nestedArray': nestedArrayId}}, function(err) {
});
From the docs,
Only one array field may appear in the query document.
The query document should only contain a single condition on the array field
being projected.
Multiple conditions may override each other
internally and lead to undefined behavior.
Under these requirements,
the following query is incorrect:
db.collection.find( { <array>: <value>, <someOtherArray>: <value2> },
{ "<array>.$": 1 } )
The solution is to modify your code to fire two queries:
Get the _ids of the documents, which match our condition.
Then perform the update.
Sample Code flow:
A.find({'arrayA._id': arrayAId, arrayB: {$in: [arrayContainsSomeArrayBIds]}},
function(err,data){
data.forEach(function(doc){
A.update({'arrayA._id': arrayAId,
"_id":doc._id},
{$push: {'arrayA.$.nestedArray': nestedArrayId}},
function(err) {
});
})
});
Related
An update in the array of objects inside another array of objects.
mongodb field that I'm working on:
otherFields: values,
tasks: [
{
_id: mongodb.objectID(),
title: string,
items:[{
_id: mongodb.objectID(),
title: string,
completed: boolean //field need to be update.
}]
},
{}...
],
otherFields: value
sample mongodb document
I need to find the document using the task_id and the item_id and update a completed field in item of a task. Using the mongoose findOneAndUpdate method
const path = "tasks.$.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
I am not sure how I need to do what I'm wanting to do. My schemas are like this:
var userObj = mongoose.Schema({
'timestamp':{type: Date, default: Date.now()},
'password':{type:String, required:true},
"userName":{type:String, required:true, unique:true}
});
var groupSchema = mongoose.Schema({
'creator':String,
'members':Array, //contains the _id of users added to the group
'admins':Array,
'name':String,
'timestamp':{type: Date, default: Date.now()},
'description':String
});
Where the members schema has an array that contains IDs of users. I need to take the array from the group document and get back user names.
I started out with a loop using the mongoose .find() method and pushing the result into an array - but as I expected the array is empty outside of the scope of the callback function.
var dat = [];
for(var i = 0; i<passed.payload.length;i++){
user.find({'_id':passed.payload[i]},'userName',function(err,result){
if(err){
console.log(err);
}else{
dat.push(result);
}
})
}
//res.send(dat)
console.log(dat);
I am not sure how to do this - I considered using .find to pull all user IDs then running the array to return back only matches. That seems like a waste of resources to pull the full users table then test it.
Is there a more complex query I can use with mongoose to pull data like this using an array of _ids to match?
Have you considered using the $in operator?
db.users.find( { userName: { $in: ["Paul", "Jenna" ] } } )
This should be more efficient and removes the loop as well.
here a link to the MongoDB docs
https://docs.mongodb.com/manual/reference/operator/query/in/#op._S_in
The reason you are getting an empty array outside for loop is mongoose queries are asynchronous (in your case User.find()) and therefore for loop will be completed before mongoose queries are completed resulting into empty array you are getting. You can handle this either by using promises or some npm module like async.
However, as #karlkurzer suggested you don't need to loop through an array here, you can instead use $in operator. Above code can be replaced with,
user.find({'_id': {$in: passed.payload}},'userName',function(err,results){
if(err){
console.log(err);
}else{
console.log(results); //You will get array of user names here
}
});
and you should get an array of userNames associated with ids you passed in callback.
Hope this helps!
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(//...
});
click here more details
I am working through a MEAN stack tutorial. It contains the following code as a route in index.js. The name of my Mongo collection is brandcollection.
/* GET Brand Complaints page. */
router.get('/brands', function(req, res) {
var db = req.db;
var collection = db.get('brandcollection');
collection.find({},{},function(e,docs){
res.render('brands', {
"brands" : docs
});
});
});
I would like to modify this code but I don't fully understand how the .find method is being invoked. Specifically, I have the following questions:
What objects are being passed to function(e, docs) as its arguments?
Is function(e, docs) part of the MongoDB syntax? I have looked at the docs on Mongo CRUD operations and couldn't find a reference to it. And it seems like the standard syntax for a Mongo .find operation is collection.find({},{}).someCursorLimit(). I have not seen a reference to a third parameter in the .find operation, so why is one allowed here?
If function(e, docs) is not a MongoDB operation, is it part of the Monk API?
It is clear from the tutorial that this block of code returns all of the documents in the collection and places them in an object as an attribute called "brands." However, what role specifically does function(e, docs) play in that process?
Any clarification would be much appreciated!
The first parameter is the query.
The second parameter(which is optional) is the projection i.e if you want to restrict the contents of the matched documents
collection.find( { qty: { $gt: 25 } }, { item: 1, qty: 1 },function(e,docs){})
would mean to get only the item and qty fields in the matched documents
The third parameter is the callback function which is called after the query is complete. function(e, docs) is the mongodb driver for node.js syntax. The 1st parameter e is the error. docs is the array of matched documents. If an error occurs it is given in e. If the query is successful the matched documents are given in the 2nd parameter docs(the name can be anything you want).
The cursor has various methods which can be used to manipulate the matched documents before mongoDB returns them.
collection.find( { qty: { $gt: 25 } }, { item: 1, qty: 1 })
is a cursor you can do various operations on it.
collection.find( { qty: { $gt: 25 } }, { item: 1, qty: 1 }).skip(10).limit(5).toArray(function(e,docs){
...
})
meaning you will skip the first 10 matched documents and then return a maximum of 5 documents.
All this stuff is given in the docs. I think it's better to use mongoose instead of the native driver because of the features and the popularity.
I have the following model:
var followerSchema = new Schema({
id_follower: {type: Schema.Types.ObjectId, ref: 'Users'},
id_post: {type: Schema.Types.ObjectId, ref: 'Posts'}
});
I want to be able to find all posts for a list of followers. When I use find, it returns me of course multiple times the same post as multiple users can follow the same post.
So I tried to use distinct, but I have the feeling the "populate" does not work afterwards.
Here is my code:
followerModel
.distinct('id_post',{id_follower:{$in:followerIds}})
.populate('id_post')
.sort({'id_post.creationDate':1})
.exec(function (err, postFollowers) {
console.log(postFollowers);
})
It only returns me the array of the posts, and it is not populated.
I am new to mongoDB, but according to the documentation of mongoose, the "distinct" method should return a query, just as the "find" method. And on a query you can execute the "populate" method, so I don't see what I am doing wrong.
I also tried to use the .distinct() method of the query, so then my code was like this:
followerModel
.find({id_follower:{$in:followerIds}})
.populate('id_post')
.distinct('id_post')
.sort({'id_post.creationDate':1})
.exec(function (err, postFollowers) {
console.log(postFollowers);
})
In that case it works, but as in the documentation of mongoose you need to provide a callback function when you use the distinct method on a query, and so in my logs I get errors all over. A workaround would be to have a dummy callback function, but I want to avoid that...
Does anybody has an idea why the first attempt is not working? And if the second approach is acceptable by providing a dummy callback?
Would this be the right way considering the current lack of support in mongoose?
followerModel
.find({id_follower:{$in:followerIds}})
.distinct('id_post',function(error,ids) {
Posts.find({'_id':{$in : ids}},function(err,result) {
console.log(result);
});
});
You can simply use aggregate to group and populate the collection.
now we have the desired result
db.<your collection name>.aggregate([
{
$match: {<match your fields here>}
},
{
$group: {_id: <your field to group the collection>}
},
{
$lookup: {
from: "<your collection of the poupulated field or referenced field>",
localField: "<give the id of the field which yout want to populate from the collection you matched above cases>",
foreignField: "_id", //this references the id of the document to match the localField id in the from collection
as: 'arrayName', //<some name to the returned document, this is a single document array>
}
},
{
$project: {
//you really don't want the whole populated fields, you can select the fields you want
<field name>:
<1 or 0>, // 1 to select and 0 to not select
//you can add multiple fields here
//to select the fields that just returned from the last stage we can use
"arrayName._id": <1 or 0>,
}
}
])
//at last you can return the data
.then((data) =>{
console.log(data);
});
we have distinct() by $group and
populate() by $lookup
and we also select() by $project