class ActiveRecord::Relation::HashMerger

:nodoc:

def initialize(relation, hash) 

def initialize(relation, hash)
  hash.assert_valid_keys(*Relation::VALUE_METHODS)
  @relation = relation
  @hash     = hash
end

def merge 

def merge
  Merger.new(relation, other).merge
end

def other

the values.
build a relation to merge in rather than directly merging
interpolation might take place for where values. So we should
Applying values to a relation has some side effects. E.g. 
def other
  other = Relation.new(relation.klass, relation.table)
  hash.each { |k, v|
    if k == :joins
      if Hash === v
        other.joins!(v)
      else
        other.joins!(*v)
      end
    else
      other.send("#{k}!", v)
    end
  }
  other
end