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module Arel
class Expression < Attribute
include Sql::Quoting
attr_reader :attribute, :function_sql
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
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
def to_sql(formatter = nil)
"#{function_sql}(#{attribute.to_sql})" + (@alias ? " AS #{quote_column_name(@alias)}" : '')
end
def aggregation?
true
end
def ==(other)
self.class == other.class and
attribute == other.attribute and
function_sql == other.function_sql and
ancestor == other.ancestor and
@alias == other.alias
end
end
end
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