module ActiveRecord::SpawnMethods

def except(*skips)

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

Removes from the query the condition(s) specified in +skips+. 
def except(*skips)
  relation_with values.except(*skips)
end

def merge(other, *rest)

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

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

Procs will be evaluated by merge:

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

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

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

def merge!(other, *rest) # :nodoc:

:nodoc: 
def merge!(other, *rest) # :nodoc:
  options = rest.extract_options!
  if other.is_a?(Hash)
    Relation::HashMerger.new(self, other, options[:rewhere]).merge
  elsif other.is_a?(Relation)
    Relation::Merger.new(self, other, options[:rewhere]).merge
  elsif other.respond_to?(:to_proc)
    instance_exec(&other)
  else
    raise ArgumentError, "#{other.inspect} is not an ActiveRecord::Relation"
  end
end

def only(*onlies)

Post.order('id asc').only(:where, :order) # uses the specified order
Post.order('id asc').only(:where) # discards the order condition

Removes any condition from the query other than the one(s) specified in +onlies+. 
def only(*onlies)
  relation_with values.slice(*onlies)
end

def relation_with(values) 

def relation_with(values)
  result = spawn
  result.instance_variable_set(:@values, values)
  result
end

def spawn # :nodoc:

:nodoc:
This is overridden by Associations::CollectionProxy 
def spawn # :nodoc:
  already_in_scope?(klass.scope_registry) ? klass.all : clone
end