How to use multiple populate fields in mongoose?

How to use multiple populate fields in mongoose?

As you can see, wherever I needed more than one field of a document populated, I encased the populate key in an array and provided an array of objects, each object having a different path. Most robust and concise way to do it, in my opinion. Latest mongoose v5.9.15 has ability to take array of populate fields so you can do,

Which is an example of a population in mongoose?

Population is the process of automatically replacing the specified paths in the document with document(s) from other collection(s). We may populate a single document, multiple documents, plain object, multiple plain objects, or all objects returned from a query. Let’s look at some examples.

Is there a way to chain populate in mongoose?

In case of array of documents, if documents are not found, it will be an empty array. You can chain populate method for populating multiple fields. If two populate methods, populate same field, second populate overrides the first one. First things first.

How to reference users in posts in mongoose?

Posts can be written by users and the can by commented by users. In this example, well reference the users in posts and comments by their ObjectId reference. The UserSchemais implemented straight forward and looks like this: varmongoose =require(‘mongoose’);

Can a query populate be used in mongoose?

In Mongoose, I can use a query populate to populate additional fields after a query. I can also populate multiple paths, such as However, this would generate a lookup on book gathering the fields for title, pages and director – and also a lookup on movie gathering the fields for title, pages and director as well.

How to reference another schema in mongoose Stack Overflow?

Addendum: No one mentioned “Populate” — it is very much worth your time and money looking at Mongooses Populate Method : Also explains cross documents referencing With this syntax, you should be able to reference your userSchema as a type in your postSchema like so:

What happens when there is no document in mongoose?

Mongoose populate doesn’t behave like conventional SQL joins. When there’s no document, story.author will be null. This is analogous to a left join in SQL. If you have an array of authors in your storySchema, populate () will give you an empty array instead. What if we only want a few specific fields returned for the populated documents?

Is there a limit to the number of fans in mongoose?

If you were to populate () using the limit option, you would find that the 2nd story has 0 fans: That’s because, in order to avoid executing a separate query for each document, Mongoose instead queries for fans using numDocuments * limit as the limit. If you need the correct limit, you should use the perDocumentLimit option (new in Mongoose 5.9.0).

Why does populate always return NULL in mongoose?

Firstly this happens when you add populate method after creating some collections. You can make new request and create new collections for the connected models (all). Then populate method should work. Previously created models will still send null but newly created collections should return populated data.

How to populate array of objects in MongoDB?

Here are lists are an array of objects (list). In JS you can access this like that, and MongoDB syntax is 99% similar to JS syntax. so you can also populate this using lists.list. Thanks for contributing an answer to Stack Overflow!

What kind of schema is a mongoose schema?

I have a Mongoose schema with an array lists of objects that consist of a reference to another collection and a nested array of numbers:

Firstly this happens when you add populate method after creating some collections. You can make new request and create new collections for the connected models (all). Then populate method should work. Previously created models will still send null but newly created collections should return populated data.

How does the population function work in mongoose?

Population is the process of automatically replacing the specified paths in the document with document (s) from other collection (s). We may populate a single document, multiple documents, plain object, multiple plain objects, or all objects returned from a query.

How to populate the Friends array in mongoose?

Specify the populate option to tell mongoose to populate the friends array of all the user’s friends: Let’s say you have a schema representing events, and a schema representing conversations. Each event has a corresponding conversation thread. In the above example, events and conversations are stored in separate MongoDB databases.