realm-js: Writing performance regression in 10.12

How frequently does the bug occur?

All the time

Description

Hi, while updating my app from 10.11 to 10.13, I found that writing times for one of the tables increased up to 20x.

While debugging, I’ve managed to create a reproducible example and nailed down that the first affected version is 10.12 and that having an array of strings in the schema is causing it.

The example is based on Realm’s TS Example

Task.ts

class Task {
  static generate(id) {
    return {
      id: id.toString(),
      triggeredOn: [
        'Monday',
        'Tuesday',
        'Wednesday',
        'Thursday',
        'Friday',
        'Saturday',
        'Sunday',
      ],
    }
  }

  static schema = {
    name: 'Task',
    primaryKey: 'id',
    properties: {
      id: 'string',
      triggeredOn: 'string[]',
    },
  };
}

export default Task;

and then the writing code:

const config = {
  schema: [Task.schema],
  deleteRealmIfMigrationNeeded: true
};
const realm = await Realm.open(config);
const start = new Date();
realm.write(() => {
  Array.from({length: 100}, (_, i) => {
    realm.create('Task', Task.generate(i), 'modified');
  });
 });
console.log('Writing Finished', new Date().getTime() - start.getTime());

For version < 10.12, I have about 1-2ms for writing, on 10.12+, it doesn’t go below 23-25.

Stacktrace & log output

No response

Can you reproduce the bug?

Yes, always

Reproduction Steps

No response

Version

10.12

What SDK flavour are you using?

Local Database only

Are you using encryption?

No, not using encryption

Platform OS and version(s)

iOS 15.2

Build environment

React Native 0.67.3

Cocoapods version

No response