module ActiveRecord::SpawnMethods

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

Post.order('id asc').except(:order)                  # removes the order condition
Post.where('id > 10').order('id asc').except(:where) # removes the where condition but keeps the order

# File activerecord/lib/active_record/relation/spawn_methods.rb, line 59
def except(*skips)
  relation_with values.except(*skips)
end

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.

# 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

Keeps only the condition(s) specified in onlies in the query, removing all others.

Post.order('id asc').only(:where)         # keeps only the where condition, removes the order
Post.order('id asc').only(:where, :order) # keeps only the where and order conditions

# File activerecord/lib/active_record/relation/spawn_methods.rb, line 67
def only(*onlies)
  relation_with values.slice(*onlies)
end