I'm working with Mongoose for the first time and I'm trying to accomplish what seems to be a simple task. I have a users document that contains a clients property, which consists of an array of client id's. As an example, my document looks like this:
{
email: "nick#movementstrategy.com",
password: "$2a$10$xZVzMYgyoyT.biOMDrBlRe3HNHY5A6lXga6uc8b/cnIAX/khQ7ep2",
modified: ISODate("2013-01-16T00:13:56.894Z"),
created: ISODate("2013-01-16T00:13:56.894Z"),
_id: ObjectId("50f5f0c4d6bbbcc6ce000002"),
clients: [
"50f6e118e0ccf9a1e9000001",
"50f6e12be0ccf9a1e9000002"
],
__v: 0
}
I've created a middleware that removes dependencies for a client when I call remove();
clientSchema.pre('remove', function(next) {
Sweepstakes.remove({client_id: this._id}).exec();
Submission.remove({client_id: this._id}).exec();
// find users with this._id present in clients, and remove from array
next();
});
Now, I simply need to locate all users who have the client id present in clients, remove the id, and update the user.
I know that I could easily query for all users with the id present, and then loop through and save out each user individually... But that seems inefficient, and my gut tells me that there is a better way to accomplish what I am trying to do -- just having a hard time locating it in the documentation.
What is the most efficient way to do this using Mongoose?
Probably something like this:
Users.update({condition}, {$pull : { clients: this._id} }, function(err, numAffected) {
//handle errors and whatever
next();
});
You can add clients : {$in : [this._id]} as condition to limit the update.
Related
I am using Passport.js for Express, which already holds the current user in the session variable req.user.
Yet when I try to update a MongoDB database I can only use req.user to identify the current user in certain cases. In others, I have to first do a root search to identify the correct user. Why?
I'm updating a database with this structure:
User A
Stocks [array]
Notes [array]
User B
Stocks [array]
Notes [array]
User C
...
Let's say we have already populated the database with 'stocks', and with 'notes' belonging to these 'stocks'. Now the user clicks a button to delete an existing 'note'.
This code works fine:
await User.updateOne (
{ $and: [ { email: req.user.email }, { 'stocks.ticker': req.body.ticker } ]},
{ $pull: { 'stocks.$.notes': { _id: req.body.id }}}
)
This query contains both the email to identify the user, and the stock's ticker to identify the relevant stock. And then the note is pulled from that stock. As said, it works fine.
But since I already know the current user (set in Passport's req.user variable) I don't want to have to include the email in the query and waste resources finding the current user.
I want to reduce to this:
await req.user.updateOne (
{ 'stocks.ticker': req.body.ticker },
{ $pull: { 'stocks.$.notes': { _id: req.body.id }}}
)
But this does not work, and I don't understand why.
If I use the req.user variable for a simpler pull action, it does work. I.e. the following code works to pull a stock document from the user's database:
await req.user.updateOne (
{ $pull: { stocks: { ticker: req.body.ticker }}}
)
But if I include a query before the pull action, it does not. I have tried everything I can think of to solve this. No joy.
I begin with mongoose and I have to use watch() method on a collection.
When i want to catch insert, there are no problems.
Nevertheless, when I want to retrieve the changes of an update, I don't know why, in some cases, mongoose changes the name of my fields?
registration.watch(). on('change', data => {
if(data.operationType == "update") {
console.log(data.updateDescription.updatedFields);
}
)};
my registration's collection is made up of persons who can accept or decline an invitation, and a person can change they answer. So it's basically a removal of the person from one array of data to be put in the other one.
The only problem I have is my array's name sometimes "change" :
{
__v: 100,
accepted: [
{
_id: 5faa76d048dd6e0017e631d4,
user: 5faa752848dd6e0017e631d2
},
{
_id: 5faa9ab06048a20017774610,
user: 5fa8fabc60260ec31606d71e
},
],
'declined.1': { _id: 5faf037a141f030017863484, user: 5faa74de48dd6e0017e631d0 },
for example here, my field declined change to "declined.1", why it's happening ? and how to avoid this ? or at least, how can i get declined's array in this situation ?
When you update a document in MongoDB, it only writes the deltas to the operations log, which is what the watch function pulls from.
The dot notation declined.1 means index 1 of the declined array. The change document you provided would be expected from pushing a new object onto the declined array. Essentially, it is saving space by not repeating all of the array elements that didn't change.
If you need to retrieve the entire document, you could set the fullDocument to updateLookup. See http://mongodb.github.io/node-mongodb-native/3.0/api/Collection.html#watch
I’m using Mongoose version 4.6.8 and MongoLab (MLab). I have a Mongoose schema called “Group” that has a collection of User subdocuments called “teachers”:
var GroupSchema = new Schema({
//…more properties here…//
teachers: [{
type: Schema.ObjectId,
ref: 'User'
}]
});
This is a document from the “groups” collection on MongoLab:
{
//…more properties here…//
"teachers": [
{
"$oid": "5799a9c759feea9c208c004c"
}
]
}
And this is a document from the “users” collection on MongoLab:
{
//…more properties here…//
"username": "bob"
}
But if I want to get a list of Groups that have a particular teacher (User) with the username of “bob”, this doesn’t work (the list of groups is empty):
Group.find({"teachers.username": "bob"}).exec(callback);
This also returns no items:
Group.find().where('teachers.username').equals('bob').exec(callback);
How can I achieve this?
Without some more knowledge of your set up (specifically whether you want anybody named Bob or a specific Bob whose id you could pick up first) - this might be some help although I think it would require you to flatten your teachers array to just their ID's, not single-key objects.
User.findById(<Id of Bob>, function(err, user){
Group.find({}, function(err, groups){
var t = groups.map(function(g){
if(g['teachers'].indexOf(user.id))
return g
})
// Do something with t
})
})
You can use populate to do that.
Try this:
Group.find({})
.populate({
path : 'teachers' ,
match : { username : "bob" }
})
.exec(callback);
populate will populate based on the teachers field (given path) and match will return only those who have username bob.
For more information on mongoose populate options, Please read Mongoose populate documentation.
I think the solution in this case is to get a teacher’s groups through the User module instead of my first inclination which was to go through the Groups module. This makes sense because it is in line with how modern APIs represent a one-to-many relationship.
As an example, in Behance’s API, an endpoint for a user’s projects is:
GET /v2/users/user/projects
And a request to this endpoint (where the User’s username is “matiascorea”) would look like this:
https://api.behance.net/v2/users/matiascorea/projects?client_id=1234567890
So in my case, instead of finding the groups by teacher, I would need to simply find the User (teacher) by username, populate the teacher’s groups, and use them:
User.findOne({username: 'bob'})
.populate('groups')
.exec(callback);
And the API call for this would be:
GET /api/users/user/groups
And a request to this endpoint would look like this:
https://example.com/api/users/bob/groups
Question: When creating something like a simple many to many friendship in mongoose, I know how to create it on ONE object, for instance, the code below in the controller shows that I am finding one user, and pushing to his friends array another user, being referenced via ObjectId.
In this way, when I look at the Json file, I can see user with _id of "57ed2e8c9cf3083c2ccec173", has a new friend in his friend's array, and I can run a population to get that friend user document. However, user who was added as a friend does not have these capabilities because his array of friends is still empty.
I know there are multiple ways to go about this, as I have read the docs, which say I could simply now push user 1 into user 2's friends array, but, in the words of the docs: "It is debatable that we really want two sets of pointers as they may get out of sync. Instead we could skip populating and directly find() the stories we are interested in."
In other words, if you have an event model with many users, and user model with many events, and you need to access the array of users from the event document, and the array of events from the user document... Would it be best to just push each instance into each other?
Is this the correct way of thinking?
Thanks
```
app.post('/friendships', function(req, res) {
User.findOne({
_id: "57ed2e8c9cf3083c2ccec173"
}, function(err, user1) {
User.findOneAndUpdate({
_id: "57ed2ebbedcd96a4536467f7"
}, {$push: {friends: user1 }}, {upsert: true}, function(err, user2) {
console.log("success");
})
})
});
```
Yes, this is the correct way of thinking, considering the limitations of Mongo for that sort of data.
When you store such an information in two places, you need to make sure that it is consistent - i.e. either it is present in both places or not. You don't have transactions in Mongo so the only way you can do it is to chain the requests and manually roll back the first one if the second one failed, hoping that it's possible to do (which may not be the case - if the second update failed because you lost a connection to the database, there is a good chance that your rollback will fail as well, in which case your database is left in an inconsistent state).
An alternative would be to store only one half of the relationship - e.g. only store events in users, but no users in events, using your example. That way the data would be consistently stored in one place but then if you wanted to get a list of users for a certain event, you'd have to make a possibly expensive database lookup instead of having it already present in the event document.
In practice in most cases I have seen storing data in two places and trying to keep them consistent.
Though it is usually done with storing documents IDs, so instead of:
{$push: {friends: user1}}
it's usually:
{$push: {friends: user1._id}}
(or just using the _id if you have it in the first place)
And instead of $push you can use $addToSet - see: https://docs.mongodb.com/manual/reference/operator/update/addToSet/
Here is a basic concept of adding a two-directional friendship between id1 and id2:
function addFriendship(id1, id2) {
User.findOneAndUpdate({_id: id1}, {$addToSet: {friends: id2}}, err => {
if (err) {
// failure - no friendship added
} else {
// first friendship added, trying the second:
User.findOneAndUpdate({_id: id2}, {$addToSet: {friends: id1}}, err => {
if (err) {
// second friendship not added - rollback the first:
User.findOneAndUpdate({_id: id1}, {$pull: {friends: id2}}, err => {
if (err) {
// we're screwed
} else {
// rolled back - consistent state, no friendship
}
});
} else {
// success - both friendships added
}
});
}
});
}
Not pretty and not bulletproof but that's the most you can hope for with a database with no transactions where denormalized data is the norm.
(Of course friendship don't always work that way that they have to be bidirectional, but this is just an example of a pattern that is common for any many-to-many relationaship.)
I am having a rather interesting problem using mongoDB's $addToSet to an array full of ObjectIds.
In my mongoose schema ("Happening"), I declare an array of ObjecIds called "expected", to be used by .populate().
expected: [{type: Schema.Types.ObjectId, ref: "User" }]
... which works nicely everywhere I use it. So far so good.
I then attempt to update the Happening.expected array using $addToSet as outlined here:
http://docs.mongodb.org/manual/reference/operator/addToSet/
like so:
app.get("/happening/yamobethere/:id", ensureLoggedIn("/login"),
function (req, res) {
// userId is the mongo ObjectId of the user record
var userId = req.session.user.id,
eventId = req.params.id;
models.Happening.update(
{_id: eventId}, {
$addToSet: {expected: userId}
},
function(err, updated){
if (err) {
res.json({"error": err});
}
res.json({"updated": updated});
});
});
... which always yields:
{updated: 1}
Now the docs lead me to expect the actual userId that I passed in, so the "1" is a bit odd. I expected it to be a fail, and in light of the weirdness that happens next, it appears to be a mongodb error of some sort percolating it's way back to me as results.
The weirdness is, when I check my database, I see that indeed a new ObjectId has been added: just not the one I passed in.
"expected" : [
ObjectId("51cb18623ade2b9f1e000004"),
ObjectId("51cdb7c12f0e58bdb3000001")
],
becomes
"expected" : [
ObjectId("51cb18623ade2b9f1e000004"),
ObjectId("51cdb7c12f0e58bdb3000001"),
ObjectId("51cdb80e09612bfab3000002")
],
The new ObjectId does not appear in any of my collections. It appears to be an orphan, but I'm a mongo noob, so I may be full of compost on this.
I did attempt to cast the userId as an ObjectId:
$addToSet: {expected: mongoose.Types.ObjectId.fromString(userId)}
but that changed nothing, and really should not be necessary, since the schema should handle it.
I'd really rather not resort to downloading the entire object, appending the value to the "expected" array, then sending the whole schmear back for an update.
Any help appreciated, folks. Thanks!
Update:
A colleague suggested the following technique:
var addMe = {$addToSet: {expected: userId}};
models.Happening.findByIdAndUpdate(eventId, addMe, function(err, me) {
if (err) {
return json(err);
}
res.json(200, me);
});
... which is a bit of an improvement, since it actually returns an object for me to inspect. Unfortunately, it also results in orphaned ObjecIds appearing in the array, rather than the existing userId value I specified.
Thanks again!
It appears that my passport strategy is returning the ObjectID of the rejected attempted creation of a new user in the db via data from oauth. So, the code is fine, my data is garbage.
Never trust anything, and be prepared to look like a boob. :-)
Thanks for the clarification on my return values JohnnyHK.