Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with
or
.
Download ZIP
Browse files

When preloading has_and_belongs_to_many associations, we should only …

…instantiate one AR object per actual record in the database. (Even when IM is off.)
  • Loading branch information...
commit 73c0b390b3a1ea9487c3f667352463a90af6dd71 1 parent a5ef8b9
@jonleighton jonleighton authored
View
6 activerecord/lib/active_record/associations/preloader/has_and_belongs_to_many.rb
@@ -31,10 +31,12 @@ def association_key
private
# Once we have used the join table column (in super), we manually instantiate the
- # actual records
+ # actual records, ensuring that we don't create more than one instances of the same
+ # record
def associated_records_by_owner
+ records = {}
super.each do |owner_key, rows|
- rows.map! { |row| klass.instantiate(row) }
+ rows.map! { |row| records[row[klass.primary_key]] ||= klass.instantiate(row) }
end
end
View
16 activerecord/test/cases/associations/eager_test.rb
@@ -525,6 +525,22 @@ def test_eager_with_has_and_belongs_to_many_and_limit
assert posts[1].categories.include?(categories(:general))
end
+ # This is only really relevant when the identity map is off. Since the preloader for habtm
+ # gets raw row hashes from the database and then instantiates them, this test ensures that
+ # it only instantiates one actual object per record from the database.
+ def test_has_and_belongs_to_many_should_not_instantiate_same_records_multiple_times
+ welcome = posts(:welcome)
+ categories = Category.includes(:posts)
+
+ general = categories.find { |c| c == categories(:general) }
+ technology = categories.find { |c| c == categories(:technology) }
+
+ post1 = general.posts.to_a.find { |p| p == posts(:welcome) }
+ post2 = technology.posts.to_a.find { |p| p == posts(:welcome) }
+
+ assert_equal post1.object_id, post2.object_id
+ end
+
def test_eager_with_has_many_and_limit_and_conditions_on_the_eagers
posts = authors(:david).posts.find(:all,
:include => :comments,
Please sign in to comment.
Something went wrong with that request. Please try again.