I am developing a web application using MEAN stack.
In my application User performs a calculation operation ,
I am using mongodb map reduce and writing the output to a collection in DB (say calculated_result)so that user can see the result later,
Hence I have created a dynamic MR output collection named Calculated_result_userID.
Now the problem is "How can i defined a dynamic schema for this Collection"
I am using MONGOOSE
Eg.
var variableCollectionName = "calculated_result_"+userId;
mongoose.model(variableCollectionName, mySchema);
Thanks in adavance
Related
Suppose I am inserting data in MongoDB as
db.collection.insertMany([{username:'Jack',msg:'hello'},{username:'Jenny',msg:'hello world'},{username:'Rose',msg:'Hi howz You'}])
now I want this data to be inserted as this:
{account_username:'Jack',msg:'hello'}
{account_username:'Jenny',msg:'hello world'}
{account_username:'Rose',msg:'Hi howz You'}
and NOT THIS:
{username:'Jack',msg:'hello'}
{username:'Jenny',msg:'hello world'}
{username:'Rose',msg:'Hi howz You'}
I am using mongoose in my NodeJS code, can I do something in Schema so whenever input is username it will automatically refer to account_username of my defined mongoose Schema.
If using mongoose with mongoDB one can easily do this using mongoose virtual functions functionality, Mongoose Virtuals
Mongoose Viruals have Setters and Getters, Which have functionality to define columns with different name
I am working with SailsJs+MongoDB API. I have to create New colletion in mongoDB .Name of colletion will be in request Parameter.
example:
Suppose I want to create 'Users' collection in 'mongoDbDatabase' database
by following request.
{
"collectionName" : "Users",
"dbName" :"mongoDbDatabase"
}
Now is there any way to create dynamic collection in mongoDB using req.param('collectionName) variable ?
To use all the tools that Sails provides, you have to add code (before you start your app) for each Model / Collection you are planning to interact with. As a result, creating a collection dynamically will mean you can't take advantage of the whole data - framework sails provides.
Are you sure you need a dynamic collection? Why not a defined collection differentiated by attributes?
If you really need to do this from Sails, it looks like you can get access to the underlying raw mongo database:
var db = AnyModel.getDatastore().manager; // the database will be as defined in config/models.js or config/connections.js
var collectionName = 'Widgets';
db.createCollection(collectionName);
// note, even if this works, something like 'Widgets.find' will not.
I'm using MongoDB and Mongoose in a REST API. Some deployments require a replica set, thus separate read/write databases, so as a result I have separate read/write connections in the API. However, more simple deployments don't need a replica-set, and in those cases I point my read/write connections to the same MongoDB instance and database.
My general approach is to create all models for both connections at API start up. Even when read/write conns are connecting to same database, I am able to create the same models on both connections without error.
let ReadUser = dbRead.model('User', userSchema);
let WriteUser = dbWrite.model('User', userSchema);
// no error even when dbRead and dbWrite point to same DB
Trouble comes when until I start using Mongoose Discriminators.
let ReadSpecialUser = ReadUser.discriminator('SpecialUser', specialUserSchema);
let WriteSpecialUser = WriteUser.discriminator('SpecialUser', specialUserSchema);
// Results in this Error when read and write point to same DB:
// Error: Discriminator with name "SpecialUser" already exists
I'm look for an elegant way to deal with this. Is there a way to query the db for discriminators that are already in use?
According to the Mongoose API docs the way to do this is to use Model.discriminators. So in the case above it would be
ReadUser.discriminators
or
WriteUser.discriminators
However this doesn't return anything for me. What does work is using
Object.keys(Model.discriminators)
As expected this gets you an array of strings of the discriminator names you've set previously.
If you want to use the existing discriminator model and know its name what you can do is use Model.discriminators.discriminatorName. In your example it would be:
let ReadSpecialUserDocument = new ReadUser.discriminators.SpecialUser({
key: value,
key: value,
});
ReadSpecialUserDocument.save()
This can be useful when you need to reuse the discriminator at different times, and its name is tied to your data in some way.
While using Meteor, I sometimes access the underlying Node Mongo driver so I can make bulk updates and inserts.
const bulk = Coll.rawCollection().initializeOrderedBulkOp();
bulk.insert({key_id: Mongo.Collection.ObjectID()}); // note key_id is an ObjectID
...
bulk.execute();
But the value of the key_id fields ends up being the plain subdocument {_str: '...'} when I look in the database after the insert.
Is there any way to use bulk operations in Node's Mongo library (whatever it is Meteor uses) and keep ObjectID's as Mongo's ObjectID type?
(There's many posts about the nature of the different ID types, and explaining Minimongo, etc. I'm interested specifically about the bulk operations converting ObjectID's into plain objects, and solving that issue.)
From Neil's top-level comment
On a native method you would actually need to grab the native implementation. You should be able to access from the loaded driver through MongoInternals [...]
Mongo.Collection.ObjectID is not a plain ObjectId representation, and is actually a complex object for Meteor internal use. Hence why the native methods don't know how to use the value.
So if you have some field which is an ObjectId, and you're using some method of a Meteor Collection's rawCollection (for example,
.distinct
.aggregate
.initializeOrderedBulkOp
.initializeUnorderedBulkOp
), you'll want to convert your ObjectId's using
const convertedID = new MongoInternals.NpmModule.ObjectID(
originalID._str
);
// then use in one of the arguments to your function or something
const query = {_id: convertedID};
before calling the method on them.
I just want to know if when I set a mongoose connection and I define some models, (previously adding their appropriate requires on app.js, or wathever), the model, if not exist, will be created automatically the first time when I run node app.js?
Is this kind of logic correct?
If not, do I have to create before my mongoDB collections, models and so on?
I was thinking to an automatic creation of the mongo db collection when I first run the app.js
Thanks!
Michele Prandina
Schemas (and models) are a client-side (node.js) manifestation of your data model. A few things, like the indexes you've defined, are created upon first use (like saving a document for example). Nearly everything else is delay created, including collections.
If you want consistent behavior regarding your models (and their associated schemas), you'll need to make sure they're loaded prior to any access of the associated database. It doesn't really matter where you put them, as long as they are created/executed prior to usage. You might for example:
app.js
models\Cheese.js
\Cracker.js
Then, in app.js:
var Cheese = require('Cheese.js');
var Cracker = require('Cracker.js');
Assuming, of course, you've exported the models:
model.exports = mongoose.model('Cheese',
new mongoose.Schema({
name: String,
color: String
})
);