use set_server_option if possible

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -559,14 +559,32 @@ module ActiveRecord
         end
 
         def with_multi_statements
-          previous_flags = @config[:flags]
-          @config[:flags] = Mysql2::Client::MULTI_STATEMENTS
-          reconnect!
+          if supports_set_server_option?
+            @connection.set_server_option(Mysql2::Client::OPTION_MULTI_STATEMENTS_ON)
+          elsif !supports_multi_statements?
+            previous_flags = @config[:flags]
+            @config[:flags] = Mysql2::Client::MULTI_STATEMENTS
+            reconnect!
+          end
 
           yield
         ensure
-          @config[:flags] = previous_flags
-          reconnect!
+          unless supports_multi_statements?
+            if supports_set_server_option?
+              @connection.set_server_option(Mysql2::Client::OPTION_MULTI_STATEMENTS_OFF)
+            else
+              @config[:flags] = previous_flags
+              reconnect!
+            end
+          end
+        end
+
+        def supports_multi_statements?
+          (@config[:flags] & Mysql2::Client::MULTI_STATEMENTS) != 0
+        end
+
+        def supports_set_server_option?
+          @connection.respond_to?(:set_server_option)
         end
 
         def initialize_type_map(m = type_map)

activerecord/test/cases/fixtures_test.rb

@@ -114,6 +114,21 @@ class FixturesTest < ActiveRecord::TestCase
         end
       end
     end
+
+    def test_bulk_insert_with_a_multi_statement_query_in_a_nested_transaction
+      fixtures = {
+        "traffic_lights" => [
+          { "location" => "US", "state" => ["NY"], "long_state" => ["a"] },
+        ]
+      }
+
+      ActiveRecord::Base.transaction do
+        con = ActiveRecord::Base.connection
+        assert_equal 1, con.open_transactions
+        con.insert_fixtures_set(fixtures)
+        assert_equal 1, con.open_transactions
+      end
+    end
   end
 
   if current_adapter?(:Mysql2Adapter)