activerecord all


rails 3
```rb
1.9.3-p551 :044 > Post.all.class
Post Load (4.6ms) SELECT "posts".* FROM "posts"
=> Array

1.9.3-p551 :046 > Post.scoped.class
=> ActiveRecord::Relation
```

rails 4 scoped 启用了

2.2.3 :004 > Post.all.class
 => Post::ActiveRecord_Relation 
2.2.3 :005 > Post.where(nil).class
 => Post::ActiveRecord_Relation 
2.2.3 :006 > 

where(nil) rails 3 rails 4 通用