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require 'set'
module Arel
class Attribute
attr_reader :relation, :name, :alias, :ancestor
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 original_relation
relation.relation_for(self)
end
def original_attribute
original_relation[self]
end
def format(object)
object.to_sql(formatter)
end
def to_sql(formatter = Sql::WhereCondition.new(relation))
formatter.attribute self
end
def ==(other)
self.class == other.class and
name == other.name and
@alias == other.alias and
relation == other.relation and
ancestor == other.ancestor
end
module Transformations
def self.included(klass)
alias_method :eql?, :==
end
def hash
name.hash + history.size.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, ancestor.history].flatten : [])
end
def match?(other)
!(history & other.history).empty?
end
def /(other)
if other then (history & other.history).size.to_f / Set.new(history + other.history).size
else 0
end
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
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
private
def formatter
Sql::Attribute.new(self)
end
end
end
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