Rocket.Chat/server/startup/migrations/v196.js

import { addMigration } from '../../lib/migrations';
import { LivechatDepartmentAgents } from '../../../app/models/server';

const removeOrphanDepartmentAgents = async () => {
	const orphanAgentIds = (
		await LivechatDepartmentAgents.model
			.rawCollection()
			.aggregate([
				{
					$lookup: {
						from: 'rocketchat_livechat_department',
						localField: 'departmentId',
						foreignField: '_id',
						as: 'departments',
					},
				},
				{
					$unwind: {
						path: '$departments',
						preserveNullAndEmptyArrays: true,
					},
				},
				{ $match: { departments: { $exists: false } } },
			])
			.toArray()
	).map((dept) => dept._id);
	LivechatDepartmentAgents.remove({ _id: { $in: orphanAgentIds } });
};

addMigration({
	version: 196,
	up() {
		Promise.await(removeOrphanDepartmentAgents());
	},
});