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require 'set'
module Arel
class Attribute
attributes :relation, :name, :alias, :ancestor
deriving :==
delegate :engine, :christener, :to => :relation
def initialize(relation, name, options = {})
@relation, @name, @alias, @ancestor = relation, name, options[:alias], options[:ancestor]
end
def named?(hypothetical_name)
(@alias || name).to_s == hypothetical_name.to_s
end
def aggregation?
false
end
def column
original_relation.column_for(self)
end
def format(object)
object.to_sql(Sql::Attribute.new(self))
end
def to_sql(formatter = Sql::WhereCondition.new(relation))
formatter.attribute self
end
module Transformations
def self.included(klass)
klass.send :alias_method, :eql?, :==
end
def hash
@hash ||= history.size + name.hash + relation.hash
end
def as(aliaz = nil)
Attribute.new(relation, name, :alias => aliaz, :ancestor => self)
end
def bind(new_relation)
relation == new_relation ? self : Attribute.new(new_relation, name, :alias => @alias, :ancestor => self)
end
def to_attribute
self
end
end
include Transformations
module Congruence
def history
@history ||= [self] + (ancestor ? ancestor.history : [])
end
def join?
relation.join?
end
def root
history.last
end
def original_relation
@original_relation ||= original_attribute.relation
end
def original_attribute
@original_attribute ||= history.detect { |a| !a.join? }
end
def find_correlate_in(relation)
relation[self] || self
end
def descends_from?(other)
history.include?(other)
end
def /(other)
other ? (history & other.history).size : 0
end
end
include Congruence
module Predications
def eq(other)
Equality.new(self, other)
end
def lt(other)
LessThan.new(self, other)
end
def lteq(other)
LessThanOrEqualTo.new(self, other)
end
def gt(other)
GreaterThan.new(self, other)
end
def gteq(other)
GreaterThanOrEqualTo.new(self, other)
end
def matches(regexp)
Match.new(self, regexp)
end
def in(array)
In.new(self, array)
end
end
include Predications
module Expressions
def count(distinct = false)
distinct ? Expression.new(self, "DISTINCT").count : Expression.new(self, "COUNT")
end
def sum
Expression.new(self, "SUM")
end
def maximum
Expression.new(self, "MAX")
end
def minimum
Expression.new(self, "MIN")
end
def average
Expression.new(self, "AVG")
end
end
include Expressions
end
end
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