Added cascading eager loading that allows for queries like Author.find(:all,...

Added cascading eager loading that allows for queries like Author.find(:all, :include=> { :posts=> :comments }), which will fetch all authors, their posts, and the comments belonging to those posts in a single query (using LEFT OUTER JOIN) #3913 [anna@wota.jp]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3769 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* Added cascading eager loading that allows for queries like Author.find(:all, :include=> { :posts=> :comments }), which will fetch all authors, their posts, and the comments belonging to those posts in a single query (using LEFT OUTER JOIN) #3913 [anna@wota.jp]. Examples:
+
+    # cascaded in two levels
+    >> Author.find(:all, :include=>{:posts=>:comments})
+    => authors
+         +- posts
+              +- comments
+    
+    # cascaded in two levels and normal association
+    >> Author.find(:all, :include=>[{:posts=>:comments}, :categorizations])
+    => authors
+         +- posts
+              +- comments
+         +- categorizations
+    
+    # cascaded in two levels with two has_many associations
+    >> Author.find(:all, :include=>{:posts=>[:comments, :categorizations]})
+    => authors
+         +- posts
+              +- comments
+              +- categorizations
+    
+    # cascaded in three levels
+    >> Company.find(:all, :include=>{:groups=>{:members=>{:favorites}}})
+    => companies
+         +- groups
+              +- members
+                   +- favorites
+    
 * Make counter cache work when replacing an association #3245 [eugenol@gmail.com]
 
 * Make migrations verbose [Jamis Buck]

activerecord/test/associations_cascaded_eager_loading_test.rb

+require 'abstract_unit'
+require 'active_record/acts/list'
+require 'fixtures/post'
+require 'fixtures/comment'
+require 'fixtures/author'
+require 'fixtures/category'
+require 'fixtures/categorization'
+require 'fixtures/mixin'
+require 'fixtures/company'
+require 'fixtures/topic'
+require 'fixtures/reply'
+
+class CascadedEagerLoadingTest < Test::Unit::TestCase
+  fixtures :authors, :mixins, :companies, :posts, :categorizations, :topics
+
+  def test_eager_association_loading_with_cascaded_two_levels
+    authors = Author.find(:all, :include=>{:posts=>:comments}, :order=>"authors.id")
+    assert_equal 2, authors.size
+    assert_equal 5, authors[0].posts.size
+    assert_equal 1, authors[1].posts.size
+    assert_equal 9, authors[0].posts.collect{|post| post.comments.size }.inject(0){|sum,i| sum+i}
+  end
+
+  def test_eager_association_loading_with_cascaded_two_levels_and_one_level
+    authors = Author.find(:all, :include=>[{:posts=>:comments}, :categorizations], :order=>"authors.id")
+    assert_equal 2, authors.size
+    assert_equal 5, authors[0].posts.size
+    assert_equal 1, authors[1].posts.size
+    assert_equal 9, authors[0].posts.collect{|post| post.comments.size }.inject(0){|sum,i| sum+i}
+    assert_equal 1, authors[0].categorizations.size
+    assert_equal 1, authors[1].categorizations.size
+  end
+
+  def test_eager_association_loading_with_cascaded_two_levels_with_two_has_many_associations
+    authors = Author.find(:all, :include=>{:posts=>[:comments, :categorizations]}, :order=>"authors.id")
+    assert_equal 2, authors.size
+    assert_equal 5, authors[0].posts.size
+    assert_equal 1, authors[1].posts.size
+    assert_equal 9, authors[0].posts.collect{|post| post.comments.size }.inject(0){|sum,i| sum+i}
+  end
+
+  def test_eager_association_loading_with_cascaded_two_levels_and_self_table_reference
+    authors = Author.find(:all, :include=>{:posts=>[:comments, :author]}, :order=>"authors.id")
+    assert_equal 2, authors.size
+    assert_equal 5, authors[0].posts.size
+    assert_equal authors(:david).name, authors[0].name
+    assert_equal [authors(:david).name], authors[0].posts.collect{|post| post.author.name}.uniq
+  end
+
+  def test_eager_association_loading_with_cascaded_two_levels_with_condition
+    authors = Author.find(:all, :include=>{:posts=>:comments}, :conditions=>"authors.id=1", :order=>"authors.id")
+    assert_equal 1, authors.size
+    assert_equal 5, authors[0].posts.size
+  end
+
+  def test_eager_association_loading_with_acts_as_tree
+    roots = TreeMixin.find(:all, :include=>"children", :conditions=>"mixins.parent_id IS NULL", :order=>"mixins.id")
+    assert_equal [mixins(:tree_1), mixins(:tree2_1), mixins(:tree3_1)], roots
+    assert_equal 2, roots[0].children.size
+    assert_equal 0, roots[1].children.size
+    assert_equal 0, roots[2].children.size
+  end
+
+  def test_eager_association_loading_with_cascaded_three_levels_by_ping_pong
+    firms = Firm.find(:all, :include=>{:account=>{:firm=>:account}}, :order=>"companies.id")
+    assert_equal 2, firms.size
+    assert_equal firms.first.account, firms.first.account.firm.account
+    assert_equal companies(:first_firm).account, firms.first.account.firm.account
+    assert_equal companies(:first_firm).account.firm.account, firms.first.account.firm.account
+  end
+
+  def test_eager_association_loading_with_sti
+    topics = Topic.find(:all, :include => :replies, :order => 'topics.id')
+    assert_equal [topics(:first), topics(:second)], topics
+    assert_equal 1, topics[0].replies.size
+    assert_equal 0, topics[1].replies.size
+  end
+end

activerecord/test/associations_go_eager_test.rb

@@ -92,15 +92,15 @@ def test_eager_association_loading_with_belongs_to_and_limit_and_offset_and_cond
   end
 
   def test_eager_association_loading_with_belongs_to_and_limit_and_multiple_associations
-    posts = Post.find(:all, :include => [:author, :very_special_comment], :limit => 1)
+    posts = Post.find(:all, :include => [:author, :very_special_comment], :limit => 1, :order => 'posts.id')
     assert_equal 1, posts.length
-    assert_equal [4], posts.collect { |p| p.id }
+    assert_equal [3], posts.collect { |p| p.id }
   end
   
   def test_eager_association_loading_with_belongs_to_and_limit_and_offset_and_multiple_associations
-    posts = Post.find(:all, :include => [:author, :very_special_comment], :limit => 1, :offset => 1)
-    assert_equal 0, posts.length
-    assert_equal [], posts
+    posts = Post.find(:all, :include => [:author, :very_special_comment], :limit => 1, :offset => 1, :order => 'posts.id')
+    assert_equal 1, posts.length
+    assert_equal [4], posts.collect { |p| p.id }
   end
   
   def test_eager_with_has_many_through