Bug#12809202 61854: MYSQLDUMP --SINGLE-TRANSACTION

--FLUSH-LOG BREAKS CONSISTENCY

The transaction started by mysqldump gets committed
implicitly when flush-log is specified along with
single-transaction option, and hence can break
consistency.

This is because, COM_REFRESH is executed in order
to flush logs and starting from 5.5 this command
performs an implicit commit.

Fixed by making sure that COM_REFRESH is executed
before the transaction has started and not after it.

Note : This patch triggers following behavioral
       changes in mysqldump :

1) After this patch we no longer flush logs before
   dumping each database if --single-transaction
   option is given like it was done before (in the
   absence of --lock-all-tables and --master-data
   options).

2) Also, after this patch, we start acquiring
   FTWRL before flushing logs in cases when only
   --single-transaction and --flush-logs are given.
   It becomes safe to use mysqldump with these two
   options and without --master-data parameter for
   backups.


client/mysqldump.c:
  Bug#12809202 61854: MYSQLDUMP --SINGLE-TRANSACTION
               --FLUSH-LOG BREAKS CONSISTENCY
  
  Added logic to make sure that, if flush-log option
  is specified, mysql_refresh() is never executed after
  the transaction has started.
  
  Added verbose messages for all the executions of
  mysql_refresh() in order to track its invocation.
mysql-test/r/mysqldump.result:
  Added test case for Bug#12809202.
mysql-test/t/mysqldump.test:
  Added test case for Bug#12809202.

mysql-test/r/mysqldump.result

@@ -4662,3 +4662,103 @@ UNLOCK TABLES;
 /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
 
 DROP TABLE t1;
+#
+# Bug#12809202 61854: MYSQLDUMP --SINGLE-TRANSACTION --FLUSH-LOG BREAKS
+#                     CONSISTENCY
+#
+DROP DATABASE IF EXISTS b12809202_db;
+CREATE DATABASE b12809202_db;
+CREATE TABLE b12809202_db.t1 (c1 INT);
+CREATE TABLE b12809202_db.t2 (c1 INT);
+INSERT INTO b12809202_db.t1 VALUES (1), (2), (3);
+INSERT INTO b12809202_db.t2 VALUES (1), (2), (3);
+# Starting mysqldump with --single-transaction & --flush-log options..
+# Note : In the following dump the transaction
+#        should start only after the logs are
+#        flushed, as 'flush logs' causes implicit
+#        commit starting 5.5.
+
+#### Dump starts here ####
+-- Connecting to localhost...
+-- main : logs flushed successfully!
+-- Starting transaction...
+-- Retrieving table structure for table t1...
+-- Sending SELECT query...
+-- Retrieving rows...
+--
+-- Host: localhost    Database: b12809202_db
+-- ------------------------------------------------------
+
+/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
+/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
+/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
+/*!40101 SET NAMES utf8 */;
+/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;
+/*!40103 SET TIME_ZONE='+00:00' */;
+/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
+/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
+/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
+/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
+
+--
+-- Table structure for table `t1`
+--
+
+DROP TABLE IF EXISTS `t1`;
+/*!40101 SET @saved_cs_client     = @@character_set_client */;
+/*!40101 SET character_set_client = utf8 */;
+CREATE TABLE `t1` (
+  `c1` int(11) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1;
+/*!40101 SET character_set_client = @saved_cs_client */;
+
+--
+-- Dumping data for table `t1`
+--
+
+LOCK TABLES `t1` WRITE;
+/*!40000 ALTER TABLE `t1` DISABLE KEYS */;
+INSERT INTO `t1` VALUES (1),(2),(3);
+-- Retrieving table structure for table t2...
+-- Sending SELECT query...
+-- Retrieving rows...
+/*!40000 ALTER TABLE `t1` ENABLE KEYS */;
+UNLOCK TABLES;
+
+--
+-- Table structure for table `t2`
+--
+
+DROP TABLE IF EXISTS `t2`;
+/*!40101 SET @saved_cs_client     = @@character_set_client */;
+/*!40101 SET character_set_client = utf8 */;
+CREATE TABLE `t2` (
+  `c1` int(11) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1;
+/*!40101 SET character_set_client = @saved_cs_client */;
+
+--
+-- Dumping data for table `t2`
+--
+
+LOCK TABLES `t2` WRITE;
+/*!40000 ALTER TABLE `t2` DISABLE KEYS */;
+INSERT INTO `t2` VALUES (1),(2),(3);
+/*!40000 ALTER TABLE `t2` ENABLE KEYS */;
+UNLOCK TABLES;
+-- Disconnecting from localhost...
+/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;
+
+/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
+/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
+/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
+/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
+/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
+/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
+/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
+
+-- Dump completed
+#### Dump ends here ####
+DROP TABLE b12809202_db.t1;
+DROP TABLE b12809202_db.t2;
+DROP DATABASE b12809202_db;