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module Arel
class Expression < Attribute
attributes :attribute, :function_sql, :alias, :ancestor
deriving :==
delegate :relation, :to => :attribute
alias_method :name, :alias
def initialize(attribute, function_sql, aliaz = nil, ancestor = nil)
@attribute, @function_sql, @alias, @ancestor = attribute, function_sql, aliaz, ancestor
end
def to_sql(formatter = Sql::SelectClause.new(relation))
formatter.expression self
end
def aggregation?
true
end
module Transformations
def as(aliaz)
Expression.new(attribute, function_sql, aliaz, self)
end
def bind(new_relation)
new_relation == relation ? self : Expression.new(attribute.bind(new_relation), function_sql, @alias, self)
end
def to_attribute
Attribute.new(relation, @alias, :ancestor => self)
end
end
include Transformations
end
end
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