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.

1 files changed, 32 insertions, 0 deletions

diff --git a/mysql-test/t/mysqldump.test b/mysql-test/t/mysqldump.test
index e224bf6afe3..b1688986090 100644
--- a/mysql-test/t/mysqldump.test
+++ b/mysql-test/t/mysqldump.test
@@ -2215,5 +2215,37 @@ CREATE TABLE t1 (a INT);
 --exec $MYSQL_DUMP --compatible=no_t,no_f --skip-comments test
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#12809202 61854: MYSQLDUMP --SINGLE-TRANSACTION --FLUSH-LOG BREAKS
+--echo #                     CONSISTENCY
+--echo #
+
+--disable_warnings
+DROP DATABASE IF EXISTS b12809202_db;
+--enable_warnings
+
+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);
+
+--echo # Starting mysqldump with --single-transaction & --flush-log options..
+--echo # Note : In the following dump the transaction
+--echo #        should start only after the logs are
+--echo #        flushed, as 'flush logs' causes implicit
+--echo #        commit starting 5.5.
+--echo
+--echo #### Dump starts here ####
+--replace_regex /-- Server version.*// /-- MySQL dump .*// /-- Dump completed on .*/-- Dump completed/
+--exec $MYSQL_DUMP --verbose --single-transaction --flush-log b12809202_db 2>&1
+--echo
+--echo #### Dump ends here ####
+
+DROP TABLE b12809202_db.t1;
+DROP TABLE b12809202_db.t2;
+DROP DATABASE b12809202_db;
+
 # Wait till we reached the initial number of concurrent sessions
 --source include/wait_until_count_sessions.inc