How to get the defined indexes from Mongoose

In Mongoose, each model has a schema associated with it, which defines the structure and configuration of the documents, including indexes. If you want to retrieve the defined indexes of a model, you can call the indexes method of the model's schema.

Below is a specific step-by-step example demonstrating how to retrieve defined indexes in Mongoose:

Assume we have a user model defined as follows:

javascript
const mongoose = require('mongoose');
const { Schema } = mongoose;

const userSchema = new Schema({
  username: { type: String, unique: true },
  email: { type: String, unique: true },
  age: Number
});

// Add compound index
userSchema.index({ username: 1, age: -1 });

const User = mongoose.model('User', userSchema);

In this example, we define unique indexes for the username and email fields, and a compound index for username and age.

Now, if you want to retrieve all defined indexes for this model, you can use the following code:

javascript
const indexes = User.schema.indexes();
console.log(indexes);

This will output something similar to the following:

plaintext
[
  [{ username: 1 }, { unique: true, background: true }],
  [{ email: 1 }, { unique: true, background: true }],
  [{ username: 1, age: -1 }, { background: true }]
]

As shown above, the indexes() method returns an array where each element is an array with two elements. The first element represents the index keys and direction, while the second element contains the index options (e.g., unique and background).

This method is highly effective for understanding the indexing configuration in your database model and is invaluable for optimizing queries and ensuring data integrity.