Methods

Instance Public methods

except(*skips)

Removes from the query the condition(s) specified in skips.

Post.order('id asc').except(:order)                  # discards the order condition
Post.where('id > 10').order('id asc').except(:where) # discards the where condition but keeps the order
📝 Source code 
# File activerecord/lib/active_record/relation/spawn_methods.rb, line 75
    def except(*skips)
      relation_with values.except(*skips)
    end
🔎 See on GitHub

merge(other, *rest)

Merges in the conditions from other, if other is an ActiveRecord::Relation. Returns an array representing the intersection of the resulting records with other, if other is an array.

Post.where(published: true).joins(:comments).merge( Comment.where(spam: false) )
# Performs a single join query with both where conditions.

recent_posts = Post.order('created_at DESC').first(5)
Post.where(published: true).merge(recent_posts)
# Returns the intersection of all published posts with the 5 most recently created posts.
# (This is just an example. You'd probably want to do this with a single query!)

Procs will be evaluated by merge:

Post.where(published: true).merge(-> { joins(:comments) })
# => Post.where(published: true).joins(:comments)

This is mainly intended for sharing common conditions between multiple associations.

For conditions that exist in both relations, those from other will take precedence. To find the intersection of two relations, use QueryMethods#and.

📝 Source code 
# File activerecord/lib/active_record/relation/spawn_methods.rb, line 33
    def merge(other, *rest)
      if other.is_a?(Array)
        records & other
      elsif other
        spawn.merge!(other, *rest)
      else
        raise ArgumentError, "invalid argument: #{other.inspect}."
      end
    end
🔎 See on GitHub

only(*onlies)

Removes any condition from the query other than the one(s) specified in onlies.

Post.order('id asc').only(:where)         # discards the order condition
Post.order('id asc').only(:where, :order) # uses the specified order
📝 Source code 
# File activerecord/lib/active_record/relation/spawn_methods.rb, line 83
    def only(*onlies)
      relation_with values.slice(*onlies)
    end
🔎 See on GitHub