Does mongoose createIndex: false mean indexes will be created in the background or not at all?

0
votes

Mongoose docs

When your application starts up, Mongoose automatically calls createIndex for each defined index in your schema. Mongoose will call createIndex for each index sequentially, and emit an 'index' event on the model when all the createIndex calls succeeded or when there was an error. While nice for development, it is recommended this behavior be disabled in production since index creation can cause a significant performance impact. Disable the behavior by setting the autoIndex option of your schema to false, or globally on the connection by setting the option autoIndex to false.

The docs don't seem to address what happens when we set autoIndex: false. Will indexes be created in the background or do I have to write another program or script to make sure indexes are done properly in production?

Does this apply to all these scenarios the same?

  • default index like _id
  • indexes on createdAt like someCollection.index({ createdAt: 1 })
  • indexes created inline like new Schema({ someData: { type: String, default: '', index: true}).

This thread implies we can use db.ensureIndex({ name: 1 }, { background: true }); But when I look for similar syntax in the mongoose docs I only found the following

const userSchema = new Schema({
  email: { type: String, required: true, unique: true },
  registeredAt: { type: Date, index: true }
});

// [ [ { email: 1 }, { unique: true, background: true } ],
//   [ { registeredAt: 1 }, { background: true } ] ]
userSchema.indexes();

The commented out section has background: true but it's not inline with the schema definition like email: { type: String, required: true, unique: true, background: true },. I don't understand what they are trying to convey there.

This thread says that ...an index build can happen in the "background"... but I don't see this confirmed in the mongoose documentation. Maybe I missed it or maybe the issue is not understanding when to refer to the mongoose documentation over the mongodb documentation when my application is using mongoose to handle all mongodb actions.

1
mongodbmongoose
Try it and see what happens? – D. SM

1 Answers

1
votes

Looking here https://github.com/Automattic/mongoose/issues/5342 It appears that options { background: true } is the default when Mongoose creates indexes, and that you can override this.

As to your questions then:

Does this apply to all these scenarios the same?

  • default index like _id
  • the primary index would exist from inception of the collection
  • indexes on createdAt like someCollection.index({ createdAt: 1 })
  • yes would apply, this index would not be created with autoIndex off
  • indexes created inline like new Schema({ someData: { type: String, default: '', index: true}).
  • yes would apply, this index would not be created with autoIndex off