So I have a fairly simple piece of code as follows
db.get().collection('bars').insert({
barID: req.body.button,
}, {
$push: {
usersfbID: req.body.profileUser[0].facebookID
}
}, function(err, doc) {
if (err) {
throw err;
}
if (doc) {
console.log('Had to create a new document for this bar');
console.log(doc);
//callback(null, doc);
}
});
So, I'm just checking to see if a document for a bar exists, and if it doesn't then I create that document. And I want to insert an array for the usersfbID field so that I can store all the users going to the bar.
However, when I run the code, I don't get an error and it says the document has inserted but when the document logs, it doesn't have the userfbID field.
So what am I doing wrong? Does the $push operator only work with the update method of db? If so, how do I insert an array for that field?
Yes, it does work with the update methods
Reference > Operators > Update Operators > Array Update Operators > $push
Inserting a new entry means feeding the fields. In that case, there's no $push operation, since the array of the entry is freshly created and can be explicitly set (usersfbID:[req.body.profileUser[0].facebookID], meaning that you expect several fbId for that bar). Updating an array in an element of a collection isn't an insertion, it's an update.
So, just to provide an answer to the question I was facing..
Yes, you can only use $push or $addToSet with an update operation on a mongoDB document
Here is the way I implemented the code.
db.get().collection('bars').update({
barID: req.body.button,
}, {
$addToSet: {
usersfbID: req.body.profileUser[0].facebookID,
usersDocID: req.body.profileUser[0]._id
}
}, {
upsert: true
}, function(err, doc) {
if (err) {
console.log('There is an error here');
throw err;
}
if (doc) {
console.log('Had to create a new document for this bar');
callback(null, doc);
}
});
The upsert: true makes sure to insert a new document if the update method couldn't find the specified document.
Related
I currently have an upsert function in my project which works but my main problem is that it creates another instance of the record, and updates the new instance instead. This is the code:
router.route('/carousel/update/:_id').put(function(req, res) {
var id;
if(req.params._id == 'undefined'){
id = crypto.randomBytes(12).toString('hex');
}
else {
id = ObjectId(req.params._id)
}
db.collection('home').updateOne({"_id": id},
{$set: req.body}, {upsert: true}, (err, results) => {
if (err) throw err;
res.send(results)
console.log(req.body)
});
});
The problem:
1. It mystifies me that mongoDB takes my crypto generated _id and takes it as the new _id for the upserted document. Why is that? When {upsert: true}, isn't mongoDB supposed to generate a new _id?
2. Because of the nature of problem 1, whenever I try to update the original document, it updates the upserted document instead since they have the same _id values even though their _ids are positioned at different document levels.
In conclusion, when given a 'home' document, how do I upsert correctly without adding a new record with the same values and _ids?
Thanks for your help!
EDIT
This is the JSON body content of the document with custom generated _id using crypto:
{
"_id": "1262d480eea83567181b3206",
"header": "hello",
"subheader": "hello"
}
Whereas, this is the body content of the upserted document.
{
"_id": {
"$oid": "1262d480eea83567181b3206"
},
"header": "helloasad",
"subheader": "helloasda"
}
As observed, after upserting, it takes the same _id value of the original document but on another document level.
A possible solution/explanation based on #Ashwanth Madhav information:
In your code 'id' was being sent to the update as a String type, but the id in MongoDB is an ObjectId type:
Code will be something like that:
var id;
if(req.params._id == 'undefined'){
// 'id' NEED TO BE AN ObjectId...
// 'id' WAS BEING SENT AS A 'String'
id = ObjectId(crypto.randomBytes(12).toString('hex'));
}
else {
id = ObjectId(req.params._id)
}
var newsfeed = db.collection('newsfeed');
newsfeed.findAndModify({
_id: mongodb.ObjectId(newsfeedId)
}, {
new: true
}, {
$set: newsfeed
}, function(err, result) {
if (err) {
return reject(err);
} else {
return resolve(result.value);
}
});
I get a cyclic dependency error when i run this query on mongodb, ive read through other solutions presented in stackoverflow but cant seem to fix this error ..
this is the error message i see
You are setting the newsfeed object back to newsfeed collection. Try to include the field which needs to be updated instead of whole object.
you may added some schema restrictions on model with type
try to console the newsfeed and make sure data you are trying to update matching with schema field type
How can I atomically get the latest "rounds" record ObjectId and use that when inserting to the "deposits" collection?
This post answer says it can't be done: Is there any way to atomically update two collections in MongoDB?
Is this still true?
In process A, I want to atomically FIND the latest round id (rid) and INSERT that into deposits. The race condition is that after A finds rid, another process B might insert into rounds, so now A has an rid that isn't the latest, but is 1 behind. How can A finds rid in rounds + insert this rid into deposits (act on these 2 collections) atomically?
// GET ROUND ID (RID) OF LATEST
var rid;
db.rounds.find().limit(1).sort({$natural:-1}, function(err, latestInsertedRound){
rid = latestInsertedRound[0]._id;
print(rid, 'rid'); // if another process B inserts now, this rid is 1 behind
// INSERT INTO DEPOSITS
db.deposits.insert({uid:uid, iid:iid, rid:rid}, function(err, insertedDeposit){
print(insertedDeposit, 'insertedDeposit');
});
});
Inserting a document in Mongodb has a callback function that can be used. This callback function has a second parameter which returns the document inserted.
I tried printing the second parameter using console.log. It looks like :
{ result: { ok: 1, n: 1 },
ops:
[ { username: 'user1',
password: 'password1',
_id: 562099bae1872f58b3a22aed } ],
insertedCount: 1,
insertedIds: [ 562099bae1872f58b3a22aed ]
}
insertedIds is the array that holds the _ids of the inserted document or documents.
So you can insert your object in the second collection in the function callback of the insertion of first collection. A little confusing.
In simple terms : Insert the document in first collection. In it's callback, insert the document in the second collection.
MongoClient.connect(MONGOLAB_URI, function (err, db) {
if (err)
console.log("We have some error : " + err);
else {
db.createCollection('rounds', function (err, rounds) {
if (err) {
console.log('Error while creating rounds collection');
throw err;
}
else {
rounds.insert({ 'username' : 'user1', 'password' : 'password1' }, function(err,docsInserted){
console.log('Last document inserted id :', docsInserted.insertedIds[0]);
//inserting the document in the function callback
db.createCollection('deposits', function (err, deposits) {
if (err) {
console.log('Error while creating deposits collection');
throw err;
}
else {
//change array index according to your need
//you may be inserting multiple objects simultaneously
deposits.insert({'last_inserted_object' : docsInserted.insertedIds[0]);
console.log('inserted into deposits collection');
}
});
});
}
});
}
});
It seems it's not possible to operate atomically on 2 collections in MongoDB, as explained in this answer:
Is there any way to atomically update two collections in MongoDB?
I leave the question up because it has a slightly different focus (not 2 updates, but find+insert).
I'm getting a duplicate document when using the mongodb-native-driver to save an update to a document. My first call to save() correctly creates the document and adds a _id with an ObjectID value. A second call creates a new document with a text _id of the original ObjectID. For example I end up with:
> db.people.find()
{ "firstname" : "Fred", "lastname" : "Flintstone", "_id" : ObjectId("52e55737ae49620000fd894e") }
{ "firstname" : "Fred", "lastname" : "Flintstone with a change", "_id" : "52e55737ae49620000fd894e" }
My first call correctly created Fred Flinstone. A second call that added " with a change" to the lastname, created a second document.
I'm using MongoDB 2.4.8 and mongo-native-driver 1.3.23.
Here is my NodeJS/Express endpoint:
app.post("/contacts", function (req, res) {
console.log("POST /contacts, req.body: " + JSON.stringify(req.body));
db.collection("people").save(req.body, function (err, inserted) {
if (err) {
throw err;
} else {
console.dir("Successfully inserted/updated: " + JSON.stringify(inserted));
res.send(inserted);
}
});
});
Here is the runtime log messages:
POST /contacts, req.body: {"firstname":"Fred","lastname":"Flintstone"}
'Successfully inserted/updated: {"firstname":"Fred","lastname":"Flintstone","_id":"52e55737ae49620000fd894e"}'
POST /contacts, req.body: {"firstname":"Fred","lastname":"Flintstone with a change","_id":"52e55737ae49620000fd894e"}
'Successfully inserted/updated: 1'
Why doesn't my second update the existing record? Does the driver not cast the _id value to an ObjectID?
What you are posting back the 2nd time contains a field named "_id", and it's a string. That is the problem.
Look at the document, what the save method does is a "Simple full document replacement function". I don't use this function quit often so here's what I guess. The function use the _id field to find the document and then replace the full document with what you provided. However, what you provided is a string _id. Apparently it doesn't equal to the ObjectId. I think you should wrap it to an ObjectId before passing to the function.
Besides, the save method is not recommended according to the document. you should use update (maybe with upsert option) instead
I don't exactly know why a second document is created, but why don't you use the update function (maybe with the upsert operator)?
An example for the update operation:
var query = { '_id': '52e55737ae49620000fd894e' };
db.collection('people').findOne(query, function (err, doc) {
if (err) throw err;
if (!doc) {
return db.close();
}
doc['lastname'] = 'Flintstone with a change';
db.collection('people').update(query, doc, function (err, updated) {
if (err) throw err;
console.dir('Successfully updated ' + updated + ' document!');
return db.close();
});
});
And now with the upsert operator:
var query = { '_id': '52e55737ae49620000fd894e' };
var operator = { '$set': { 'lastname': 'Flintstone with a change' } };
var options = { 'upsert': true };
db.collection('people').update(query, operator, options, function (err, upserted) {
if (err) throw err;
console.dir('Successfully upserted ' + upserted + ' document!');
return db.close();
});
The difference is that the upsert operator will update the document if it exist, otherwise it will create a new one. When using the upsert operator you should keep in mind that this operation can be underspecified. That means if your query does not contain enough information to identify a single document, a new document will be inserted.
I know I can't use upsert and the positional operator together, but I am looking for away to append to array if some fields of the object I am inserting do not match some fields in an existing object within the array.
so if I have the existing document below, I would like to check for 'field' field's value and update/replace that subdocument if the fields match, and simply append to the array if they don't.
{
myArray:[
{
field:'xyz'
}
]
}
Is there a good way to do this in node.js? I'm using the native driver.
I don't think you can do this in a single query. You can do this with two separate queries in the native driver. The first query would try to update the field in the array. If it doesn't find the document in the array that matches, it dispatches a second query to append the document to the array.
db.collection('coll').update({_id: _id, "myArray": {field: "xyz"}}, {"$set": {"myArray.$": {field: "xyzt"}}}, {upsert: true}, function(err, res) {
if (err && err.code == 16836) { // no document was matched
db.collection('coll').update({_id: _id}, {"$push": {myArray: {field: "xyzt"}}}, function(err, res) {
console.log("Inserted document in array");
});
}
console.log("Updated document in array");
});