References table schema

Schema::create('references', function (Blueprint $
    $table->integer('model_id');
    $table->string('model_type');
    $table->integer('reference_id');
    $table->string('reference_type');
    $table->string('collection')->default('default');
    $table->timestamps();
    $table->index(['model_id', 'model_type', 'reference_id', 'reference_type']);
});