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module Arel
class Join
include Relation
attr_reader :relation1, :relation2, :predicates
def initialize(relation1, relation2 = Nil.instance, *predicates)
@relation1 = relation1
@relation2 = relation2
@predicates = predicates
@attributes = nil
end
def name
relation1.name
end
def attributes
@attributes ||= (relation1.externalize.attributes | relation2.externalize.attributes).bind(self)
end
def wheres
# TESTME bind to self?
relation1.externalize.wheres
end
def ons
@ons ||= @predicates.collect { |p| p.bind(self) }
end
# TESTME
def externalizable?
relation1.externalizable? or relation2.externalizable?
end
def join?
true
end
def engine
relation1.engine != relation2.engine ? Memory::Engine.new : relation1.engine
end
def table_sql(formatter = Sql::TableReference.new(self))
relation1.externalize.table_sql(formatter)
end
def joins(environment, formatter = Sql::TableReference.new(environment))
@joins ||= begin
this_join = [
join_sql,
relation2.externalize.table_sql(formatter),
("ON" unless predicates.blank?),
(ons + relation2.externalize.wheres).collect { |p| p.bind(environment.relation).to_sql(Sql::WhereClause.new(environment)) }.join(' AND ')
].compact.join(" ")
[relation1.joins(environment), this_join, relation2.joins(environment)].compact.join(" ")
end
end
def eval
result = []
relation1.call.each do |row1|
relation2.call.each do |row2|
combined_row = row1.combine(row2, self)
if predicates.all? { |p| p.eval(combined_row) }
result << combined_row
end
end
end
result
end
def to_sql(formatter = nil)
compiler.select_sql
end
end
class InnerJoin < Join
def join_sql; "INNER JOIN" end
end
class OuterJoin < Join
def join_sql; "LEFT OUTER JOIN" end
end
class StringJoin < Join
def joins(environment, formatter = Sql::TableReference.new(environment))
[relation1.joins(environment), relation2].compact.join(" ")
end
def externalizable?
relation1.externalizable?
end
def attributes
relation1.externalize.attributes
end
def engine
relation1.engine
end
end
end
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