Implement savepoints.

activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb

@@ -55,12 +55,14 @@ module ActiveRecord
       end
 
       # Wrap a block in a transaction.  Returns result of block.
-      def transaction(start_db_transaction = true)
+      def transaction(start_db_transaction = false)
+        start_db_transaction ||= open_transactions.zero? || (open_transactions == 1 && transactional_fixtures)
         transaction_open = false
         begin
           if block_given?
             if start_db_transaction
-              begin_db_transaction
+              open_transactions.zero? ? begin_db_transaction : create_savepoint
+              increment_open_transactions
               transaction_open = true
             end
             yield
@@ -68,21 +70,23 @@ module ActiveRecord
         rescue Exception => database_transaction_rollback
           if transaction_open
             transaction_open = false
-            rollback_db_transaction
+            decrement_open_transactions
+            open_transactions.zero? ? rollback_db_transaction : rollback_to_savepoint
           end
           raise unless database_transaction_rollback.is_a? ActiveRecord::Rollback
         end
       ensure
         if transaction_open
+          decrement_open_transactions
           begin
-            commit_db_transaction
+            open_transactions.zero? ? commit_db_transaction : release_savepoint
           rescue Exception => database_transaction_rollback
-            rollback_db_transaction
+            open_transactions.zero? ? rollback_db_transaction : rollback_to_savepoint
             raise
           end
         end
       end
-
+      
       # Begins the transaction (and turns off auto-committing).
       def begin_db_transaction()    end
 

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -159,6 +159,21 @@ module ActiveRecord
       def decrement_open_transactions
         @open_transactions -= 1
       end
+      
+      def create_savepoint
+      end
+      
+      def rollback_to_savepoint
+      end
+      
+      def release_savepoint
+      end
+      
+      def current_savepoint_name
+        "rails_savepoint_#{open_transactions}"
+      end
+      
+      attr_accessor :transactional_fixtures
 
       def log_info(sql, name, seconds)
         if @logger && @logger.debug?

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -343,6 +343,17 @@ module ActiveRecord
         # Transactions aren't supported
       end
 
+      def create_savepoint
+        execute("SAVEPOINT #{current_savepoint_name}")
+      end
+
+      def rollback_to_savepoint
+        execute("ROLLBACK TO SAVEPOINT #{current_savepoint_name}")
+      end
+
+      def release_savepoint
+        execute("RELEASE SAVEPOINT #{current_savepoint_name}")
+      end
 
       def add_limit_offset!(sql, options) #:nodoc:
         if limit = options[:limit]

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -567,6 +567,17 @@ module ActiveRecord
         end
       end
 
+      def create_savepoint
+        execute("SAVEPOINT #{current_savepoint_name}")
+      end
+
+      def rollback_to_savepoint
+        execute("ROLLBACK TO SAVEPOINT #{current_savepoint_name}")
+      end
+
+      def release_savepoint(savepoint_number)
+        execute("RELEASE SAVEPOINT #{current_savepoint_name}")
+      end
 
       # SCHEMA STATEMENTS ========================================
 

activerecord/lib/active_record/fixtures.rb

@@ -932,6 +932,7 @@ module Test #:nodoc:
           end
           ActiveRecord::Base.connection.increment_open_transactions
           ActiveRecord::Base.connection.begin_db_transaction
+          ActiveRecord::Base.connection.transactional_fixtures = true
         # Load fixtures for every test.
         else
           Fixtures.reset_cache
@@ -954,6 +955,7 @@ module Test #:nodoc:
         if use_transactional_fixtures? && ActiveRecord::Base.connection.open_transactions != 0
           ActiveRecord::Base.connection.rollback_db_transaction
           ActiveRecord::Base.connection.decrement_open_transactions
+          ActiveRecord::Base.connection.transactional_fixtures = false
         end
         ActiveRecord::Base.clear_active_connections!
       end

activerecord/lib/active_record/transactions.rb

@@ -122,14 +122,10 @@ module ActiveRecord
     # One should restart the entire transaction if a StatementError occurred.
     module ClassMethods
       # See ActiveRecord::Transactions::ClassMethods for detailed documentation.
-      def transaction(&block)
-        connection.increment_open_transactions
-
-        begin
-          connection.transaction(connection.open_transactions == 1, &block)
-        ensure
-          connection.decrement_open_transactions
-        end
+      def transaction(options = {}, &block)
+        options.assert_valid_keys :force
+        
+        connection.transaction(options[:force], &block)
       end
     end
 

activerecord/test/cases/transactions_test.rb

@@ -213,6 +213,99 @@ class TransactionTest < ActiveRecord::TestCase
     assert Topic.find(2).approved?, "Second should still be approved"
   end
 
+  def test_invalid_keys_for_transaction
+    assert_raises ArgumentError do
+      Topic.transaction :forced => true do
+      end
+    end
+  end
+
+  def test_force_savepoint_in_nested_transaction
+    Topic.transaction do
+      @first.approved = true
+      @second.approved = false
+      @first.save!
+      @second.save!
+
+      begin
+        Topic.transaction :force => true do
+          @first.happy = false
+          @first.save!
+          raise
+        end
+      rescue
+      end
+    end
+
+    assert @first.reload.approved?
+    assert !@second.reload.approved?
+  end
+
+  def test_no_savepoint_in_nested_transaction_without_force
+    Topic.transaction do
+      @first.approved = true
+      @second.approved = false
+      @first.save!
+      @second.save!
+
+      begin
+        Topic.transaction do
+          @first.approved = false
+          @first.save!
+          raise
+        end
+      rescue
+      end
+    end
+
+    assert !@first.reload.approved?
+    assert !@second.reload.approved?
+  end
+  
+  def test_many_savepoints
+    Topic.transaction do
+      @first.content = "One"
+      @first.save!
+      
+      begin
+        Topic.transaction :force => true do
+          @first.content = "Two"
+          @first.save!
+          
+          begin
+            Topic.transaction :force => true do
+              @first.content = "Three"
+              @first.save!
+              
+              begin
+                Topic.transaction :force => true do
+                  @first.content = "Four"
+                  @first.save!
+                  raise
+                end
+              rescue
+              end
+              
+              @three = @first.reload.content
+              raise
+            end
+          rescue
+          end
+          
+          @two = @first.reload.content
+          raise
+        end
+      rescue
+      end
+      
+      @one = @first.reload.content
+    end
+    
+    assert_equal "One", @one
+    assert_equal "Two", @two
+    assert_equal "Three", @three
+  end
+
   uses_mocha 'mocking connection.commit_db_transaction' do
     def test_rollback_when_commit_raises
       Topic.connection.expects(:begin_db_transaction)
@@ -282,6 +375,45 @@ class TransactionTest < ActiveRecord::TestCase
     end
 end
 
+class TransactionsWithTransactionalFixturesTest < ActiveRecord::TestCase
+  self.use_transactional_fixtures = true
+  fixtures :topics
+
+  def test_automatic_savepoint_in_outer_transaction
+    @first = Topic.find(1)
+    
+    begin
+      Topic.transaction do
+        @first.approved = true
+        @first.save!
+        raise
+      end
+    rescue
+      assert !@first.reload.approved?
+    end
+  end
+
+  def test_no_automatic_savepoint_for_inner_transaction
+    @first = Topic.find(1)
+
+    Topic.transaction do
+      @first.approved = true
+      @first.save!
+
+      begin
+        Topic.transaction do
+          @first.approved = false
+          @first.save!
+          raise
+        end
+      rescue
+      end
+    end
+
+    assert !@first.reload.approved?
+  end
+end
+
 if current_adapter?(:PostgreSQLAdapter)
   class ConcurrentTransactionTest < TransactionTest
     use_concurrent_connections