Composer not installing all the dependencies in lumen

I have installed lumen using composer but on accessing it throwing the error

In Application.php line 164:

Class 'Illuminate\Database\DatabaseServiceProvider' not found

What could be the reason for this?

Also i couldn't find DatabaseServiceProvider.php anywhere in vendor folder. I am using composer version 1.6.3 2018-01-31 16:28:17

via Chebli Mohamed