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module Arel
class Join < Relation
attr_reader :join_sql, :relation1, :relation2, :predicates
delegate :engine, :name, :to => :relation1
hash_on :relation1
def initialize(join_sql, relation1, relation2 = Nil.new, *predicates)
@join_sql, @relation1, @relation2, @predicates = join_sql, relation1, relation2, predicates
end
def ==(other)
self.class == other.class and
predicates == other.predicates and (
(relation1 == other.relation1 and relation2 == other.relation2) or
(relation2 == other.relation1 and relation1 == other.relation2)
)
end
def table_sql(formatter = Sql::TableReference.new(self))
relation1.externalize.table_sql(formatter)
end
def joins(environment, formatter = Sql::TableReference.new(environment))
this_join = [
join_sql,
relation2.externalize.table_sql(formatter),
("ON" unless predicates.blank?),
(predicates + relation2.externalize.selects).collect { |p| p.bind(environment).to_sql }.join(' AND ')
].compact.join(" ")
[relation1.joins(environment), this_join, relation2.joins(environment)].compact.join(" ")
end
def attributes
@attributes ||= (relation1.externalize.attributes +
relation2.externalize.attributes).collect { |a| a.bind(self) }
end
def selects
relation1.externalize.selects
end
# XXX
def relation_for(attribute)
[
relation1.externalize.relation_for(attribute),
relation2.externalize.relation_for(attribute)
].max do |r1, r2|
a1, a2 = r1 && r1[attribute], r2 && r2[attribute]
attribute / a1 <=> attribute / a2
end
end
# TESTME
def aggregation?
relation1.aggregation? or relation2.aggregation?
end
def join?
true
end
end
class Relation
def join?
false
end
end
end
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