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module Arel
class Expression < Attribute
attributes :attribute, :alias, :ancestor
deriving :==
delegate :relation, :to => :attribute
alias_method :name, :alias
def initialize(attribute, aliaz = nil, ancestor = nil)
@attribute, @alias, @ancestor = attribute, aliaz, ancestor
end
def aggregation?
true
end
def inspect
"<#{self.class.name} #{attribute.inspect}>"
end
module Transformations
def as(aliaz)
self.class.new(attribute, aliaz, self)
end
def bind(new_relation)
new_relation == relation ? self : self.class.new(attribute.bind(new_relation), @alias, self)
end
def to_attribute(relation)
Attribute.new(relation, @alias, :ancestor => self)
end
end
include Transformations
end
class Count < Expression; end
class Distinct < Expression; end
class Sum < Expression; end
class Maximum < Expression; end
class Minimum < Expression; end
class Average < Expression; end
end
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