I usually manipulate object by creating them unique "codes". (So I create an object with the code "test" and fetch the object back using objects.find({ code: "test" }). But I find this weird and counter-productive.
I'd like to know if it's possible to simply create a new object, and get its saved object or simply its ObjectId back once saved?
That would be nice if we could do this:
objects.save({ name: "Test Object" });
And get { ObjectId: "47cc67093475061e3d95369d", name: "Test Object" } in return.
Is there any way to do so?
Thanks!
Is this what you're looking for?
> var record = {hello:"goodbye"};
> db.test.save(record);
> record;
{ "hello" : "goodbye", "_id" : ObjectId("4f90c9106aee6e21b4e55c65") }
I do not think there is an API to get the autogenerated id back from the database, and there is also no real need:
If your "code" is really unique, you can use that as the object id.
objects.save({ _id: "test" });
The _id field does not have to be of type ObjectId, it just has to be unique. If you already have some primary key type data, you do not have to use the autogenerated id. This way, you also save one index.
If you want to use a generated ObjectId, generate it yourself before you call save:
ObjectId id = new ObjectId();
objects.save({ _id: id, something: 12345 });
Related
How to handle if document structure after production changes.
Suppose I had 500 documents like this:
{
name: ‘n1’
height: ‘h1’
}
Later if I decide to add all the documents in below format:
{
name: ‘n501’
height: ‘h501’
weight: ‘w501’
}
I am using cursor.All(&userDetails) to decode(deserialize) in Go to get the output of the query in struct userDetails. If I modify the structure of further documents and userDetails accordingly, it will fail for the first 500 documents?
How to handle this change?
If you add a new field to your struct, querying old documents will not fail. Since the old documents do not have the new field saved in MongoDB, querying them will give you struct values where the new field will be its zero value. E.g. if its type is string, it will be the empty string "", if it's an int field, it will be 0.
If it bothers you that the old documents do not have this new field, you may extend them in the mongo console like this:
db.mycoll.updateMany({ "weight": {$exists:false} }, { $set: {"weight": ""} } )
This command adds a new weight field to old documents where this field did not exist, setting them to the empty string.
How can I update a mongo document with the following requirements:
Find a document by email property:
If the document exists:
If both retrieved and new document have property A, keep property A (the retrieved one).
If retrieved document property A is null or undefined or doesn't exist, update using property A of the new object.
If the document doesn't exist
Insert the new document.
The findOneAndUpdate seems not to convey the both 3 of the requirements. Thanks.
My recommendation is to go the following path:
db.getCollection('<some-collection>').update(
{ email: 'someguy#email.com' },
{
$set: {
name: "some guy",
username: someguy,
tel: '1234'
}
},
{ upsert: true }
);
Check upsert documentation:
https://docs.mongodb.com/manual/reference/method/db.collection.update/#upsert-option
Lets go through your requirements now:
3. If the document doesn't exist, insert the new document.
Yes, it will insert new document to collection if it doesnt find the document by email. Resulting document will be combination of find condition + $set + autogenerated _id, so it will look something like this:
{
_id: ObjectId(...)
email: 'someguy#email.com'
name: "some guy",
username: someguy,
tel: '1234'
}
2. If retrieved document property A is null or undefined or doesn't exist, update using property A of the new object.
All properties provided in $set will unconditionally be persisted in the database, which also covers your requirement of updating null/undefined values
3. If both retrieved and new document have property A, keep property A (the retrieved one).
If both newly provided A and database A are the same, we dont have a problem.
If As are different, dont you want to store the new A value?
If you are afraid of nulls/undefined values, you can omit them before providing object to $set.
What is the use-case for you not wanting to update database property with newly provided value?
One use-case i can see is that you want to pass createdAt in case you are creating new record, but dont want to update that value for existing records.
If thats the case, and you know those properties in advance, you can use $setOnInsert update operator. https://docs.mongodb.com/manual/reference/operator/update/#id1
So your update query can look like this:
db.getCollection('<some-collection>').update(
{ email: 'someguy#email.com' },
{
$set: {
name: "some guy",
username: someguy,
tel: '1234'
},
$setOnInsert: {
createdAt: new Date(),
updatedAt: new Date()
}
},
{ upsert: true }
);
I hope this helps!
You need not retrieve the document for updating the property A. You can use the update API of mongo to do so. Please find the psuedo code below:
db.<collection>.update({
"$or": [
{ "PropertyA": { "$exists": false } },
{ "PropertyA": null }
]
}, {$set: {"PropertyA": "NewValue"}});
The above code is for one property, but I think you can figure out how to scale it up.
Hope this helps !!
Although I think it is a general question, I could not find a solution that matches my needs.
I have 2 Mongo collections. The 'users' collection and the second one 'dbInfos'.
Now, I have a template called 'Infos' and want the already existing fields in the Mongo collections to be presented to the user in input fields in case there is data in the collection. When no data is provided in the database yet, it should be empty.
So here is my code, which works fine until I want to capture the fields from the second collection.
Template.Infos.onRendered(function() {
$('#txtName').val(Meteor.user().profile.name);
$('#txtEmail').val(Meteor.user().emails[0].address);
});
These 2 work great.
But I don´t know how to query the infos from the collection 'dbInfos', which is not the 'users' collection. Obviously Meteor.user().country does not work, because it is not in the 'users' collection. Maybe a find({}) query? However, I don´t know how to write it.
$('#txtCountry').val( ***query function***);
Regarding the structure of 'dbInfos': Every object has an _id which is equal to the userId plus more fields like country, city etc...
{
"_id": "12345",
"country": "countryX",
"city": "cityY"
}
Additionally, how can I guarantee that nothing is presented, when the field in the collection is empty? Or is this automatic, because it will just return an empty field?
Edit
I now tried this:
dbInfos.find({},{'country': 1, '_id': 0})
I think this is the correct syntax to retrieve the country field and suppress the output of the _id field. But I only get [object Object] as a return.
you're missing the idea of a foreign key. each item in a collection needs a unique key, assigned by mongo (usually). so the key of your country info being the same as the userId is not correct, but you're close. instead, you can reference the userId like this:
{
"_id": "abc123",
"userId": "12345",
"country": "countryX",
"city": "cityY"
}
here, "abc123" is unique to that collection and assigned by mongo, and "12345" is the _id of some record in Meteor.users.
so you can find it like this (this would be on the client, and you would have already subscribed to DBInfos collection):
let userId = Meteor.userId();
let matchingInfos = DBInfos.find({userId: userId});
the first userId is the name of the field in the collection, the second is the local variable that came from the logged in user.
update:
ok, i think i see where you're getting tripped it. there's a difference between find() and findOne().
find() returns a cursor, and that might be where you're getting your [object object]. findOne() returns an actual object.
for both, the first argument is a filter, and the second argument is an options field. e.g.
let cursor = DBInfos.find({
userId: Meteor.userId()
},
{
fields: {
country: 1
}
});
this is going to:
find all records that belong to the logged in user
make only the country and _id fields available
make that data available in the form of a cursor
the cursor allows you to iterate over the results, but it is not a JSON object of your results. a cursor is handy if you want to use "{{#each}}" in the HTML, for example.
if you simply change the find() to a findOne():
let result = DBInfos.findOne({ /** and the rest **/
... now you actually have a JSON result object.
you can also do a combination of find/fetch, which works like a findOne():
let result = DBInfos.find({
userId: Meteor.userId()
},
{
fields: {
country: 1
}
}).fetch();
with that result, you can now get country:
let country = result.country;
btw, you don't need to use the options to get country. i've been assuming all this code is on the client (might be a bad assumption). so this will work to get the country as well:
let result = DBInfos.findOne({userId: Meteor.userId()});
let country = result.country;
what's going on here? it's just like above, but the result JSON might have more fields in it than just country and _id. (it depends on what was published).
i'll typically use the options field when doing a find() on the server, to limit what's being published to the client. on the client, if you just need to grab the country field, you don't really need to specify the options in that way.
in that options, you can also do things like sort the results. that can be handy on the client when you're going to iterate on a cursor and you want the results displayed in a certain order.
does all that make sense? is that what was tripping you up?
Is it good or bad practice to keep the standard "_id" generated my mongo in a document as well as my own unique identifier such as "name", or should I just replace _id generated with the actual name so my documents will look like this:
{
_id: 782yb238b2327b3,
name: "my_name"
}
or just like this:
{
_id: "my_name"
}
This depends on the scenario, there is nothing wrong with having your own unique ID, it may be string or a number, completely depends on your situation as long as its unique, the important thing is you are in charge of it. You would want to add an index to it of course.
for example i have an additional ID field which is a number called 'ID', because i required a sequential number as an identifier, another usecase may be that your migrating an application so you have to conform to a particular sequence pattern.
The sequences for the unique identifies could easily be stored in a separate document/collections.
There is no issue with using the built in _id if you have no requirement not to have a custom one, an interesting fact is that you can get the created date out of the _id. Always useful.
db.col.insert( { name: "test" } );
var doc = db.col.findOne( { name: "test" } );
var timestamp = doc._id.getTimestamp();
I am getting JSON objects through an external API in node.js and want to store them in MongoDB. I defined a model like this:
var Product = new Schema({
id: ObjectId,
name: String});
And now I'm trying to store an object:
JSONProduct = { id: 1234, name: 'The Foo Bar' };
product = new Product(JSONProduct);
product.save();
The object is stored fine in the "products" collection, but the id from the JSONProduct is replaced by a MongoDB created value:
{ "id" : ObjectId("119894980274616772006500"), "name" : "The Foo Bar" }
The main reason why I want to use my Product id over the MongoDB created one is, that I want to prevent duplicate entries for products. I get the JSON Product objects through a cronjob triggered call on an external API, including already existing ones. Maybe there is another, better way to do this?
You are defining an field as an ObjectID, but you are assigning a Number to it. To create an ObjectID you need to do something like:
new ObjectId('something');
However, in your case this is probably not the best idea. Define your model like this:
var Product = new Schema({
external_id: {type: Number, unique: true},
name: {type: String},
});
You can specify unique on a field to create a unique index for that field.
In the question you've mentioned,
The object is stored fine in the "products" collection, but the id from the JSONProduct is replaced by a MongoDB created value:
{ "id" : ObjectId("119894980274616772006500"), "name" : "The Foo Bar" }
But I think the it is created as:
{ "_id" : ObjectId("119894980274616772006500"), "name" : "The Foo Bar" }
Also, you can pass in your product id to field by name "_id", then mongo will not create any separate IDs and it'll not accept duplicate values and it'll have indexing automatically for that field.
But make sure you push unique values of product id to _id.