Based on some twitter-discussions and issues like #1817672: Use db_query() instead of db_select() where appropriate #1805996: [META] Views in Drupal Core
I'm asking now when should we use db_select and when db_query.
In Drupal 7 the policy seemed to be: use db_query only when it's performance critical code.
Based on some comments some people seems to think that in Drupal 8 you should use db_query unless:
- You have a dynamic query like a view
- You need some kind of access mechanism like node_access
- You want to do fancyness like pagerDecorators.