Find many in mongoose
Mongoose has a more powerful alternative called populate , which lets you reference documents in other collections. 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, a plain object, multiple plain objects, or all objects returned from a query. Let's look at some examples.SEE VIDEO BY TOPIC: Mongoose Schemas & Models
Mongoose findOne with Multiple Conditions
You can also create compound indexes of more than one property. Say you have some database and you would like to find all extinct animals, you would probably write a query like so Model. MongoDB will now where to look at to find relevant documents. The order in which the fields are added to the index is important.
The more requests you do the slower your app response time becomes. Try to minimise your database queries as much as possible and combine them together or ideally avoiding them at all by getting rid of duplicate or unnecessary db operations. You can also cache your database results in redis. Every property you add in your model will be returned from your queries, so if you have an array or a nested object in some of these fields, your document will easily get huge slowing down the performance of your query.
If your document includes an array of references to other Models, and you use. Its better to favour using. To prevent the database from doing extra work to return these fields increasing the size of the returned documents you can use mongoose. I wrote another article about this here. For example:. Instead, the database operations can be run in parallel using Promise. Instead you should connect once at the beginning of your app and reuse the connection. This is because setting up a new TCP connection is expensive time-wise, network request wise and memory wise, Also a new connection means a new thread to be created by MongoDB using memory on the database as well.
How much can these tips improve your query performance? I ran a local installation of MongoDB and wrote a NodeJS script that populates the database with a list of randomly generated users thanks to casual. The goal is to find users who are older than 22 years old.
I wrote the query in different ways combining the methods mentioned above and tried them on two different database collections that are populated with the same dataset. The results were measured using the console. I used casual library which is pretty handy to generate semantic mock data. With 10k users in the database. As you can see the optimised version of the query that uses. Sign in. Khaled Osman Follow. Lets write some performance tests to see the results How much can these tips improve your query performance?
Express Tutorial Part 3: Using a Database (with Mongoose)
Performance is the art of avoiding unnecessary work. This is probably the best thing you can do to improve the performance of a query. Mongoose allows you to add.
In this tutorial, I will show you how to deal with MongoDB Many to Many Relationship which is an important and complicated Relationship that you will use in most database structures. Think about a Tutorial Blog with the relationship between Tutorial and Tag that goes in both directions:. We can denormalize data into a denormalized form simply by embedding the related documents right into the main document. We need to separate documents, collections, and IDs.
Mongoose Relationships Tutorial
When working with databases, data retrieval is the most used operation of all the CRUD operations. When working with mongoose and MongoDB, documents of a collection can be retrieved using various methods. In this article, we will discuss such methods of retrieving documents from a collection in MongoDB. And we will use the postman tool for executing routes. The most common method for data retrieval in both mongoose, as well as mongo shell, is the find method. The find methods retrieve all the documents of a collection when an empty object is passed. The find method has two parameters — an object and a callback function. Here, we are passing an empty object. The callback function also has two parameters — error if any occurs and the returning value. As mentioned earlier, the find method returns all the documents when an empty object is passed.
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Mongoose models provide several static helper functions for CRUD operations. Each of these functions returns a mongoose Query object. A mongoose query can be executed in one of two ways. First, if you pass in a callback function, Mongoose will execute the query asynchronously and pass the results to the callback. When executing a query with a callback function, you specify your query as a JSON document.
The findOne method is one of the two popular methods that are used to retrieve data from MongoDB collections in mongoose. As the name suggests, the findOne methods find a single document only. Usually, we provide a query to match a document.
How find() Works in Mongoose
The exports object of the mongoose module is an instance of this class. Most apps will only use this one instance. The Mongoose Decimal SchemaType. Used for declaring paths in your schema that should be bit decimal floating points.SEE VIDEO BY TOPIC: 12 Aggregation Example 4 $group by multiple fields - MongoDB Aggregation Tutorial
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There's some confusion on the internet about what happens when you call Model. Make no mistake, Model. But there's some confusion about Model. In this article, I'll provide a conceptual overview of what happens when you call Model. For the purposes of this article, I'll assume you already have a MongoDB instance running on localhost
One will be for publishers and another will be for games. Then, we will have another collection to represent a game. So in the object here, we have a game that references the id of a publisher document. This is the reference approach.
How to optimize MongoDB & Mongoose for Performance
This page documents the mongo shell method, and does not refer to the MongoDB Node. Selects documents in a collection or view and returns a cursor to the selected documents. The projection parameter determines which fields are returned in the matching documents.