[WIP] create temporary stored procedure on MySQL deletion

lib/database_rewinder/cleaner.rb

@@ -55,7 +55,7 @@ def delete_all(ar_conn, tables, multiple: true)
           # Print the warning message, then fall back to non-multiple deletion
           Kernel.warn "WARNING: You may be executing DatabaseRewinder inside a transactional test. You're presumably misconfiguring your tests. Please read DatabaseRewinder's document, and properly configure your tests."
         else
-          ar_conn.execute_multiple tables.map {|t| "DELETE FROM #{ar_conn.quote_table_name(t)}"}.join(';')
+          ar_conn.delete_multiple tables
           return
         end
       end

lib/database_rewinder/multiple_statements_executor.rb

@@ -7,43 +7,47 @@ def supports_multiple_statements?
         %w(ActiveRecord::ConnectionAdapters::PostgreSQLAdapter ActiveRecord::ConnectionAdapters::Mysql2Adapter ActiveRecord::ConnectionAdapters::SQLite3Adapter).include? self.class.name
       end
 
-      def execute_multiple(sql)
+      def delete_multiple(tables)
         #TODO Use ADAPTER_NAME when we've dropped AR 4.1 support
         case self.class.name
         when 'ActiveRecord::ConnectionAdapters::PostgreSQLAdapter'
+          sql = tables_to_one_delete_sql tables
           disable_referential_integrity { log(sql) { @connection.exec sql } }
+
         when 'ActiveRecord::ConnectionAdapters::Mysql2Adapter'
           if @connection.query_options[:connect_flags] & Mysql2::Client::MULTI_STATEMENTS != 0
             disable_referential_integrity do
+              sql = tables_to_one_delete_sql tables
               _result = log(sql) { @connection.query sql }
               while @connection.next_result
                 # just to make sure that all queries are finished
                 _result = @connection.store_result
               end
             end
+
           else
-            query_options = @connection.query_options.dup
-            query_options[:connect_flags] |= Mysql2::Client::MULTI_STATEMENTS
-            # opens another connection to the DB
-            client = Mysql2::Client.new query_options
-            begin
-              # disable_referential_integrity
-              client.query("SET FOREIGN_KEY_CHECKS = 0")
-              _result = log(sql) { client.query sql }
-              while client.next_result
-                # just to make sure that all queries are finished
-                _result = client.store_result
-              end
-            ensure
-              client.close
+            @connection.query 'drop procedure if exists rewind_em_all'
+            @connection.query <<-SQL
+create procedure rewind_em_all(in tables text, in num integer) begin declare i int default 0; while i < num do set i = i + 1; set @delete_sql = concat('DELETE FROM ', substring_index(substring_index(tables, ',', i), ',', -1)); prepare stmt from @delete_sql; execute stmt; deallocate prepare stmt; end while; end;
+SQL
+            disable_referential_integrity do
+              @connection.query "call rewind_em_all('#{tables.join(',')}', #{tables.length})"
             end
           end
+
         when 'ActiveRecord::ConnectionAdapters::SQLite3Adapter'
+          sql = tables_to_one_delete_sql tables
           disable_referential_integrity { log(sql) { @connection.execute_batch sql } }
+
         else
           raise 'Multiple deletion is not supported with the current database adapter.'
         end
       end
+
+      private
+      def tables_to_one_delete_sql(tables)
+        tables.map {|t| "DELETE FROM #{quote_table_name(t)}"}.join(';')
+      end
     end
   end
 end