BUG#46364 MyISAM transbuffer problems (NTM problem)

It is well-known that due to concurrency issues, a slave can become
inconsistent when a transaction contains updates to both transaction and
non-transactional tables in statement and mixed modes.

In a nutshell, the current code-base tries to preserve causality among the
statements by writing non-transactional statements to the txn-cache which
is flushed upon commit. However, modifications done to non-transactional
tables on behalf of a transaction become immediately visible to other
connections but may not immediately get into the binary log and therefore
consistency may be broken.

In general, it is impossible to automatically detect causality/dependency
among statements by just analyzing the statements sent to the server. This
happen because dependency may be hidden in the application code and it is
necessary to know a priori all the statements processed in the context of
a transaction such as in a procedure. Moreover, even for the few cases that
we could automatically address in the server, the computation effort
required could make the approach infeasible.

So, in this patch we introduce the option
    - "--binlog-direct-non-transactional-updates" that can be used to bypass
    the current behavior in order to write directly to binary log statements
    that change non-transactional tables.

mysql-test/extra/rpl_tests/rpl_mixing_engines.inc:
  Backported this from Celosia to improve the test cases related to the NTM issue.
sql/log.cc:
  Checks the --binlog-direct-non-transactional-updates before choosing
  to either use the trxn-cache or not.
sql/mysqld.cc:
  Introduces the option --binlog-direct-non-transactional-updates.
sql/set_var.cc:
  Introduces the option --binlog-direct-non-transactional-updates.
sql/sql_class.h:
  Introduces the option --binlog-direct-non-transactional-updates.

1 files changed, 6 insertions, 1 deletions

diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 7bb357827c8..242acd28ecc 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -5727,7 +5727,8 @@ enum options_mysqld
   OPT_SLAVE_EXEC_MODE,
   OPT_GENERAL_LOG_FILE,
   OPT_SLOW_QUERY_LOG_FILE,
-  OPT_IGNORE_BUILTIN_INNODB
+  OPT_IGNORE_BUILTIN_INNODB,
+  OPT_BINLOG_DIRECT_NON_TRANS_UPDATE
 };
 
 
@@ -7071,6 +7072,10 @@ The minimum value for this variable is 4096.",
    (uchar**) &max_system_variables.net_wait_timeout, 0, GET_ULONG,
    REQUIRED_ARG, NET_WAIT_TIMEOUT, 1, IF_WIN(INT_MAX32/1000, LONG_TIMEOUT),
    0, 1, 0},
+  {"binlog-direct-non-transactional-updates", OPT_BINLOG_DIRECT_NON_TRANS_UPDATE,
+   "Causes updates to non-transactional engines using statement format to be written directly to binary log. Before using this option make sure that there are no dependencies between transactional and non-transactional tables such as in the statement INSERT INTO t_myisam SELECT * FROM t_innodb; otherwise, slaves may diverge from the master.",
+   (uchar**) &global_system_variables.binlog_direct_non_trans_update, (uchar**) &max_system_variables.binlog_direct_non_trans_update, 0, GET_BOOL, NO_ARG, 0,
+    0, 0, 0, 0, 0},
   {0, 0, 0, 0, 0, 0, GET_NO_ARG, NO_ARG, 0, 0, 0, 0, 0, 0}
 };