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module ActiveRelation
class Join < Relation
attr_reader :join_sql, :relation1, :relation2, :predicates
def initialize(join_sql, relation1, relation2, *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 qualify
descend(&:qualify)
end
def attributes
(externalize(relation1).attributes +
externalize(relation2).attributes).collect { |a| a.bind(self) }
end
def prefix_for(attribute)
externalize(relation1).prefix_for(attribute) or
externalize(relation2).prefix_for(attribute)
end
def descend(&block)
Join.new(join_sql, relation1.descend(&block), relation2.descend(&block), *predicates.collect(&block))
end
protected
def joins
this_join = [
join_sql,
externalize(relation2).table_sql,
"ON",
predicates.collect { |p| p.bind(self).to_sql }.join(' AND ')
].join(" ")
[relation1.joins, relation2.joins, this_join].compact.join(" ")
end
def selects
externalize(relation1).selects + externalize(relation2).selects
end
def table_sql
externalize(relation1).table_sql
end
private
def externalize(relation)
Externalizer.new(relation)
end
Externalizer = Struct.new(:relation) do
def table_sql
relation.aggregation?? relation.to_sql(Sql::Aggregation.new) : relation.send(:table_sql)
end
def selects
relation.aggregation?? [] : relation.send(:selects)
end
def attributes
relation.aggregation?? relation.attributes.collect(&:to_attribute) : relation.attributes
end
def prefix_for(attribute)
if relation[attribute]
relation.alias?? relation.alias : relation.prefix_for(attribute)
end
end
end
end
end
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