Oh I see. It seems like Rails does something smart and does not join the projects with discussions tables. The following query is used by Rails when I try it:
```SQL SELECT "discussions".* FROM "discussions" WHERE "discussions"."project_id" = $1 AND (user_id=1)  [["project_id", 4]]```
Seems like since it already has a user and a proj object when it reaches the code, it just looks for them in the discussions table.