Indicate index won't be created when not buffering

[Ehbraheem]

Updates documentation to show the caveat of turning off buffering.

Summary

Mongoose doesn't create indexes automatically when buffering is turned off. Possible reason for #10631

Examples

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

const testSchema = new Schema({
    name: String,
    age: Number,
    weight: Number,
    height: Number,
    birthday: String
});

testSchema.index({age: 1}, {unique: true});
testSchema.index({ name: 1, weight: 1});
testSchema.index({ name: 1, birthday: 1}, {unique: true});
testSchema.index({ name: 1, height: 1});

testSchema.index({'$**': 'text'}, { name: 'textIndex'});

const Test = mongoose.model('Test', testSchema, 'test');

async function test() {
    await mongoose.connect('mongodb://localhost:27017/test', {
        useNewUrlParser: true,
        useUnifiedTopology: true,
        bufferCommands: false
      });
      await mongoose.connection.dropDatabase();
      await Test.init();
    console.log(await Test.listIndexes());
}

test();

Example is taken from @IslandRhythms' #10631 (comment)

[vkarpov15]

I took a quick look and your script shows that Mongoose does in fact create indexes if bufferCommands is disabled in v6.3.2. Below is the script output:

[
  { v: 2, key: { _id: 1 }, name: '_id_' },
  {
    v: 2,
    key: { age: 1 },
    name: 'age_1',
    background: true,
    unique: true
  },
  {
    v: 2,
    key: { name: 1, weight: 1 },
    name: 'name_1_weight_1',
    background: true
  },
  {
    v: 2,
    key: { name: 1, birthday: 1 },
    name: 'name_1_birthday_1',
    background: true,
    unique: true
  },
  {
    v: 2,
    key: { name: 1, height: 1 },
    name: 'name_1_height_1',
    background: true
  },
  {
    v: 2,
    key: { _fts: 'text', _ftsx: 1 },
    name: 'textIndex',
    background: true,
    weights: { '$**': 1 },
    default_language: 'english',
    language_override: 'language',
    textIndexVersion: 3
  }
]

What version of Mongoose are you using? Based on useUnifiedTopology, it looks like you're using some 5.x version?

[javierguzman]

Hello @vkarpov15 I have just updated my project packages, including Moongose from 5.12.13 to 6.3.2. My tests have started to fail due to indexes not being created. In order to figure out what it is going on I have added this:

DestinationModel.on('index', err => {
  console.log('Destination model indexes done');
  if (err) {
    console.log(err);
  }
});

Originally, I set bufferCommands to false, but I can only see the message "Destination model indexes done" if bufferCommands is set to true

[Uzlopak]

If the collection already exists i think the indizes are not generated.

[vkarpov15]

@javierguzman can you please open a new issue and follow the issue template? bufferCommands should generate indexes.

@Uzlopak Mongoose will call createIndexes() regardless of whether the collection exists.