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module Arel
class Attribute
attr_reader :relation, :name, :alias, :ancestor
delegate :engine, :to => :relation
def initialize(relation, name, options = {})
@relation, @name, @alias, @ancestor = relation, name, options[:alias], options[:ancestor]
end
def alias_or_name
@alias || name
end
def aggregation?
false
end
module Transformations
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
def qualified_name
"#{prefix}.#{name}"
end
def column
relation.column_for(self)
end
def ==(other)
self.class == other.class and
relation == other.relation and
name == other.name and
@alias == other.alias and
ancestor == other.ancestor
end
module Congruence
def self.included(klass)
klass.hash_on :name
end
def history
[self] + (ancestor ? [ancestor, ancestor.history].flatten : [])
end
def =~(other)
!(history & other.history).empty?
end
def %(other)
if other then (history - other.history) + (other.history - history)
else history
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
def to_sql(formatter = Sql::WhereCondition.new(engine))
formatter.attribute prefix, name, self.alias
end
def format(object)
object.to_sql(formatter)
end
private
def formatter
Sql::Attribute.new(self)
end
def prefix
relation.prefix_for(self)
end
end
end
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