BookStack/database/migrations/2021_05_15_173110_create_favourites_table.php

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

return new class extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('favourites', function (Blueprint $table) {
            $table->increments('id');
            $table->integer('user_id')->index();
            $table->integer('favouritable_id');
            $table->string('favouritable_type', 100);
            $table->timestamps();

            $table->index(['favouritable_id', 'favouritable_type'], 'favouritable_index');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('favourites');
    }
};