Bug #47863 binlog_format should be writable only at transaction boundaries

When @@session.binlog_format is modified inside a transaction,
it can cause slave to go out of sync.
      
To fix the problem, make the session variable 'binlog_format' 
read-only inside a transaction.


mysql-test/suite/binlog/r/binlog_format_switch_inside_trans.result:
  Test result for bug#47863.
mysql-test/suite/binlog/t/binlog_format_switch_inside_trans.test:
  Added test file to verify if the session variable 'binlog_format' 
  is read-only inside a transaction and in sub-statements.
sql/set_var.cc:
  Added code to make the session variable 'binlog_format'
  read-only inside a transaction.

mysql-test/suite/binlog/r/binlog_format_switch_inside_trans.result

@@ -0,0 +1,90 @@
+set @save_binlog_format= @@global.binlog_format;
+create table t1 (a int) engine= myisam;
+create table t2 (a int) engine= innodb;
+SELECT @@session.binlog_format;
+@@session.binlog_format
+ROW
+SET AUTOCOMMIT=1;
+# Test that the session variable 'binlog_format' 
+# is writable outside a transaction.
+set @@session.binlog_format= statement;
+SELECT @@session.binlog_format;
+@@session.binlog_format
+STATEMENT
+begin;
+# Test that the session variable 'binlog_format' is read-only
+# inside a transaction with no preceding updates.
+set @@session.binlog_format= mixed;
+ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
+insert into t2 values (1);
+# Test that the session variable 'binlog_format' is read-only
+# inside a transaction with preceding transactional updates.
+set @@session.binlog_format= row;
+ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
+commit;
+begin;
+insert into t1 values (2);
+# Test that the session variable 'binlog_format' is read-only
+# inside a transaction with preceding non-transactional updates.
+set @@session.binlog_format= statement;
+ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
+commit;
+# Test that the session variable 'binlog_format' is writable 
+# when AUTOCOMMIT=0, before a transaction has started.
+set AUTOCOMMIT=0;
+set @@session.binlog_format= row;
+SELECT @@session.binlog_format;
+@@session.binlog_format
+ROW
+insert into t1 values (4);
+# Test that the session variable 'binlog_format' is read-only inside an
+# AUTOCOMMIT=0 transaction with preceding non-transactional updates.
+set @@session.binlog_format= statement;
+ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
+SELECT @@session.binlog_format;
+@@session.binlog_format
+ROW
+commit;
+insert into t2 values (5);
+# Test that the session variable 'binlog_format' is read-only inside an
+# AUTOCOMMIT=0 transaction with preceding transactional updates.
+set @@session.binlog_format= row;
+ERROR HY000: Cannot modify @@session.binlog_format inside a transaction
+SELECT @@session.binlog_format;
+@@session.binlog_format
+ROW
+commit;
+begin;
+insert into t2 values (6);
+# Test that the global variable 'binlog_format' is writable
+# inside a transaction.
+SELECT @@global.binlog_format;
+@@global.binlog_format
+ROW
+set @@global.binlog_format= statement;
+SELECT @@global.binlog_format;
+@@global.binlog_format
+STATEMENT
+commit;
+set @@global.binlog_format= @save_binlog_format;
+create table t3(a int, b int) engine= innodb;
+create table t4(a int) engine= innodb;
+create table t5(a int) engine= innodb;
+create trigger tr2 after insert on t3 for each row begin
+insert into t4(a) values(1);
+set @@session.binlog_format= statement; 
+insert into t4(a) values(2);
+insert into t5(a) values(3);
+end |
+# Test that the session variable 'binlog_format' is read-only
+# in sub-statements.
+insert into t3(a,b) values(1,1);
+ERROR HY000: Cannot change the binary logging format inside a stored function or trigger
+SELECT @@session.binlog_format;
+@@session.binlog_format
+ROW
+drop table t1;
+drop table t2;
+drop table t3;
+drop table t4;
+drop table t5;

mysql-test/suite/binlog/t/binlog_format_switch_inside_trans.test

@@ -0,0 +1,98 @@
+#
+# BUG#47863
+# This test verifies if the session variable 'binlog_format' 
+# is read-only inside a transaction and in sub-statements.
+#
+
+source include/have_innodb.inc;
+source include/have_binlog_format_row.inc;
+
+set @save_binlog_format= @@global.binlog_format;
+create table t1 (a int) engine= myisam;
+create table t2 (a int) engine= innodb;
+
+SELECT @@session.binlog_format;
+SET AUTOCOMMIT=1;
+--echo # Test that the session variable 'binlog_format' 
+--echo # is writable outside a transaction.
+set @@session.binlog_format= statement;
+SELECT @@session.binlog_format;
+
+begin;
+--echo # Test that the session variable 'binlog_format' is read-only
+--echo # inside a transaction with no preceding updates.
+--error ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_BINLOG_FORMAT
+  set @@session.binlog_format= mixed;
+
+  insert into t2 values (1);
+--echo # Test that the session variable 'binlog_format' is read-only
+--echo # inside a transaction with preceding transactional updates.
+--error ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_BINLOG_FORMAT
+  set @@session.binlog_format= row;
+commit;
+
+begin;
+  insert into t1 values (2);
+--echo # Test that the session variable 'binlog_format' is read-only
+--echo # inside a transaction with preceding non-transactional updates.
+--error ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_BINLOG_FORMAT
+  set @@session.binlog_format= statement;
+commit;
+
+--echo # Test that the session variable 'binlog_format' is writable 
+--echo # when AUTOCOMMIT=0, before a transaction has started.
+set AUTOCOMMIT=0;
+set @@session.binlog_format= row;
+SELECT @@session.binlog_format;
+
+insert into t1 values (4);
+--echo # Test that the session variable 'binlog_format' is read-only inside an
+--echo # AUTOCOMMIT=0 transaction with preceding non-transactional updates.
+--error ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_BINLOG_FORMAT
+set @@session.binlog_format= statement;
+SELECT @@session.binlog_format;
+commit;
+
+insert into t2 values (5);
+--echo # Test that the session variable 'binlog_format' is read-only inside an
+--echo # AUTOCOMMIT=0 transaction with preceding transactional updates.
+--error ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_BINLOG_FORMAT
+set @@session.binlog_format= row;
+SELECT @@session.binlog_format;
+commit;
+
+begin;
+  insert into t2 values (6);
+--echo # Test that the global variable 'binlog_format' is writable
+--echo # inside a transaction.
+  SELECT @@global.binlog_format;
+  set @@global.binlog_format= statement;
+  SELECT @@global.binlog_format;
+commit;
+
+set @@global.binlog_format= @save_binlog_format;
+
+create table t3(a int, b int) engine= innodb;
+create table t4(a int) engine= innodb;
+create table t5(a int) engine= innodb;
+delimiter |;
+eval create trigger tr2 after insert on t3 for each row begin
+    insert into t4(a) values(1);
+    set @@session.binlog_format= statement; 
+    insert into t4(a) values(2);
+    insert into t5(a) values(3);
+end |
+delimiter ;|
+
+--echo # Test that the session variable 'binlog_format' is read-only
+--echo # in sub-statements.
+--error ER_STORED_FUNCTION_PREVENTS_SWITCH_BINLOG_FORMAT
+insert into t3(a,b) values(1,1);
+SELECT @@session.binlog_format;
+
+drop table t1;
+drop table t2;
+drop table t3;
+drop table t4;
+drop table t5;
+

sql/set_var.cc

@@ -1244,6 +1244,14 @@ void fix_slave_exec_mode(enum_var_type type)
 
 
 bool sys_var_thd_binlog_format::check(THD *thd, set_var *var) {
+  /*
+    Make the session variable 'binlog_format' read-only inside a transaction.
+  */
+  if (thd->active_transaction() && (var->type == OPT_SESSION))
+  {
+    my_error(ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_BINLOG_FORMAT, MYF(0));
+    return 1;
+  }
   /*
     All variables that affect writing to binary log (either format or
     turning logging on and off) use the same checking. We call the

sql/share/errmsg.txt

@@ -6249,3 +6249,5 @@ ER_DEBUG_SYNC_TIMEOUT
 ER_DEBUG_SYNC_HIT_LIMIT
   eng "debug sync point hit limit reached"
   ger "Debug Sync Point Hit Limit erreicht"
+ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_BINLOG_FORMAT
+  eng "Cannot modify @@session.binlog_format inside a transaction"