Question

I have a “Profile” model and two ActiveRecord::Relations of this model. SQL request of first relation is very big. Second is

Profile.where(:id => 1)

I want to add second relation to first. So, as a result, second relation will contain first prrofile.

I tried to

first.merge(second)

but it returns empty relation. Rails version is 3.2.2
Of course, result should be relation, too. I need to add .limit() and .paginate() to this relation.

Answer 1

You can tack additional .where clauses onto an existing relation, thus:

relation = Thing.joins(:associated_things => [:users, :still_more_things]).where(:condition => true)
new_relation = relation.where(:id => 1)

This will combine the new ‘where’ with any existing one using AND. ActiveRecord::Relation doesn’t support joining ‘wheres’ with OR, if you need to do that, check out Squeel (https://github.com/ernie/squeel) if you’re on Rails 3.1+, or meta_where (https://github.com/ernie/meta_where) for 3.0.