I have an Collection Model that has a property of items that holds an array of Item Models.
const CollectionSchema = new mongoose.Schema({
title: {
type: String,
required: true
},
items : [{type : mongoose.Schema.Types.ObjectId, ref: 'Item'}]
});
I tried to populate the items array in order to get the objectId's properties, but the items array would return back empty. (The code below is how I populated the items array. I first found the collection I was looking for by the _id using the req.body.search. I then ran .populate("items") in order to populate the items array. What I got back was an empty items array.)
userRouter.post('/iList', passport.authenticate('jwt', {session: false}), (req, res) => {
Collection.findById({_id : req.body.search}).populate("items").exec((err, document) => {
if(err)
res.json(err)
else
res.json({item: document})
})
});
I know my items array isn't empty since I can check on mongoDB that it is full.
The image of my mongoDB collection with an items array that isn't empty.
The weird thing is that if I put "collections" into the .populate params, my Items array does return with stuff, but it only returns the ObjectIDs and not actual object properties. I am confused to why .populate("items") isn't working.
If you are using findById then why are you specifying {_id: req.body.search}. If your req.body.search is a type of mongoose ObjectId string then you can directly use findById(req.body.search) instead of that. Also you can use simply the projection. Second argument in find calls are projections
If you are trying get items array only then why don't you try this query:-
Collection.findById(req.body.search, {items: 1}).then((result) => {
console.log('Items are :-\n', result);
}, (err) => {
console.log(err);
})
1 means include and 0 means exclude. So items will be present in output, also _id is default in output. In case you want to exclude _id then you can change second parameter to this -> {items: 1, _id: 0}
Never mind. The issue was when I pushed the Item Models via mongoose, I forgot to do items.save() which meant the items array held nothing.
Related
I'm trying to update an array that sits inside another array in a document. The schema is like this:
const projectSchema = new mongoose.Schema({
stakeholders: [{
stakeholderTitle: {
type: String,
},
...
subgroup: [{
subgroupTitle: {
type: String
},
subgroupPercent: {
type: Number,
}
}]
}],
and I'm trying to update the 'subgroup' array. I have got the query to work on its parent (the stakeholder array) with the positional $ operator, using the answer to this question I asked previously. So my query looks like this.....
await db.findOneAndUpdate({ find by the id }, { "stakeholders.$.stakeholderTitle": req.body.stakeholderTitle, ... "stakeholders.$.subgroup": req.body.subgroup })
However, this query doesn't work for the 'stakeholders subgroup' array, and makes it null. Looking through the mongo docs for the positional operator it states that 'The positional $ operator cannot be used for queries which traverse more than one array, such as queries that traverse arrays nested within other arrays, because the replacement for the $ placeholder is a single value', which I guess might be my problem.
So how can I do this with a findOneAndUpdate query?
From what I see is you have to specify the object you want to update inside the subgroup array. Try this - (i.e I'm updating the subgroupTitle of the subgroup array);
await db.findOneAndUpdate(
{
_id: userId,
"stakeholders.stakeholderTitle": req.body.stakeholderTitle,
"stakeholders.stakeholderTitle.subgroup.subgroupTitle": req.body.subgroupTitle
},
{$set: {
"stakeholders.stakeholderTitle.subgroup.$.subgroupPercent": somePercentValue,
}
},
);
Also note, it's only the array that you find that you can update. It might not be exactly what you want, but its a step closer
I have mongo db collection that looks like this :
({
_id:id ,
createdAt: new Date(),
name:name,
friends : [{name:"tommy",children:[{name:"sarah",age:12}]}],
dogs : [{}]
});
I would like to be able to insert a new element in the friends array if the name doesnt exist and a children element to that new array.
If i'm adding a new friend named john with a child nathaly , i'd like the output to be
({
_id:id ,
createdAt: new Date(),
name:name,
friends : [{name:"tommy",children:[{name:"sarah",age:12}]},{name:"john",children:[{name:"natahly",age:20}]}],
dogs : [{}]
});
If friend tommy already exist i would like just the children to be added to the children array and the output to now be
({
_id:id ,
createdAt: new Date(),
name:name,
friends : [{name:"tommy",children:[{name:"sarah",age:12},{name:"newchild",age:99}]},{name:"john",children:[{name:"natahly",age:20}]}],
dogs : [{}]
});
I've tried so many things already it's impossible to list.
currently i'm trying a mix of everything
// if `friends` is `[]`, push the empty children firstly through addToSet
var bulk = Directory.rawCollection().initializeUnorderedBulkOp();
bulk.find({_id: id, 'friends.name': {$exists: false}}).updateOne(
{$addToSet: {friends: {name: name_var, children: []}});
Meteor.wrapAsync(bulk.execute)();
// then Since previous step create the children array for said friend only if it doesn't already exist i'm just trying to update said friend with the new child
Directory.update(
{ _id: id,"friends.name": name_var },
{ $push: { "friends.$.children": {name:"sarah",age:12}
}}})
(i've also tried with "friends.children" instead of "friends.$.children" but i just get a different error)
And this should cover my three case but i'm having issues and i'm wondering if i'm going the right way. Any of you guys have any idea because this should at least work to add the children but it doesn't..
Errors : MongoError: The field 'friends.0.children' must be an array but is of type Object in document {_id: "0"} # when friends.$.children"
MongoError: cannot use the part (Friends of Friends.childrens) to traverse the element when friends.children"
One way of doing it would be to,
Initialize the object you want to insert/update
The object can have multiple children inserted at once.
var obj = {name:"tommy",children:[{name:"ds",age:12},{name:"two",age:12}]};
Initialize the Bulk API.
The order of operations does not matter here.
var bulk = db.t.initializeUnorderedBulkOp();
Find and update only the children records that already have a sub document for the name.
use the $addToSet operator to maintain unique records, and $each to add more than one children at a time.
bulk.find({"friends.name":obj.name})
.update({$addToSet:{"friends.$.children":{$each:obj.children}}});
Find and update those which do not have a sub document.
$push the entire object if a document doesn't have one.
bulk.find({"friends.name":{$ne:obj.name}})
.update({$push:{"friends":obj}});
bulk.execute();
I'm novice to MongoDB/Mongoose. I have a bounded array for a user. How would I query for firstName: bob and update pet[0] array?
When reading examples, the query is always on the embeded document array itself, as each element value would be unique in a whole collection. Since this is not the case in my situation, I need to query on the outside document(like firstName) and then update the element by element number.
For example:
UserModel.update(
{ firstName: "bob" },
{'$set': {'pets.$.
//not going to work
You can try this one
UserModel.findOne({ firstName: "bob" }, function(err, user) {
user.pets[0] = // new pets is here.
user.save(function(err) {...});
Let's say I have the following data model in Mongo:
{
_id: ...,
name: "...",
obj: {...},
list: [ ... ],
}
Now let's say, my list array is very long, and I don't want to grab the whole document every time. So I want to get obj and name, but only grab the last 5 elements in list. How do you do this with with Mongo? I'm using pymongo.
I think you are looking for the $slice operator. Docs are here.
The syntax you are looking for is something like this:
db.coll.find({}, {obj:1, name: 1, list:{$slice: -5}}); // last 5
Note that this will also return the _id field by default. If you do not want the _id add _id:0 in front of obj:1. This is the JS syntax, but the python syntax will be very close.
use $slice operator to limit array elements
GeoLocation.find({},{name: 1, geolocation:{$slice: -5}})
.then((result) => {
res.json(result);
})
.catch((err) => {
res.status(500).json({ success: false, msg: `Something went wrong. ${err}` });
});
where geolocation is array of data, from that we get last 5 record.
I made a simple db with a few users in it with mongodb and nodejs. Next im looping through the list and display the users in the list's names etc with sys.puts().
No I am adding the users to an Array() like this:
db.open(function(err, db) {
db.collection('users', function(err, collection) {
collection.find({}, {'sort':[['name', 1]]}, function(err, cursor) {
cursor.each(function(err, user) {
if(user != null) {
users[user._id] = { 'name':user.name, 'email': user.email };
sys.puts(">> Adding user to list... "+ user.name);
}
});
db.close();
});
});
});
Is this how I add the users to the array? Because the users.lenght = 0. Im a bit lost now
What you are doing is setting properties on the array object, that might be a bit confusing.
[] is both used for indexes and keys, that means in case of your array, users[0] will return the first element in the array, but users['blaid12'] will get/set the property blaid12' on the array object, that's like doingusers.blaid12`.
So in the end your array becomes more like a hashmap. The length property does not count the properties of the object, it counts the elements in the array.
You have a couple of ways of solving the issue:
Use an object {} and use the user ids as keys on that object, you'll have to keep track of the user count via another variable.
Use the array as an array by using users.push({'name':...}) to append elements to the array, if you need the userid too, then just add it to the object you push into the array.
Go with a mixed approach, use an array to push the values, and then an object to map the ids to the array indexes.