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module ActiveRelation
class Join < Relation
attr_reader :join_sql, :relation1, :relation2, :predicates
delegate :table_sql, :to => :relation1
def initialize(join_sql, relation1, relation2, *predicates)
@join_sql, @relation1, @relation2, @predicates = join_sql, relation1, relation2, predicates
end
def ==(other)
predicates == other.predicates and
((relation1 == other.relation1 and relation2 == other.relation2) or
(relation2 == other.relation1 and relation1 == other.relation2))
end
def qualify
Join.new(join_sql, relation1.qualify, relation2.qualify, *predicates.collect(&:qualify))
end
protected
def joins
[relation1.joins, relation2.joins, join].compact.join(" ")
end
def selects
relation1.send(:selects) + relation2.send(:selects)
end
# this is magick!!!
def projections
relation1.send(:projections) + relation2.attributes
end
def attribute(name)
relation1[name] || relation2[name]
end
private
def join
"#{join_sql} #{relation2.send(:table_sql)} ON #{predicates.collect { |p| p.to_sql(Sql::Predicate.new) }.join(' AND ')}"
end
def join
[join_sql, right_table, "ON", predicates.collect { |p| p.to_sql(Sql::Predicate.new) }.join(' AND ')].join(" ")
end
def right_table
relation2.aggregation?? relation2.to_sql(Sql::Aggregation.new) : relation2.send(:table_sql)
end
end
end
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