Fix handling of "SET TRANSACTION ISOLATION LEVEL ...". (Bug #7955)

mysql-test/r/bdb.result:
  Add results
mysql-test/t/bdb.test:
  Add new test
sql/set_var.cc:
  Refuse attempts to change tx_isolation while a transaction is in progress.
sql/set_var.h:
  Support check function for sys_var_thd_enum
sql/share/errmsg.txt:
  Add new error message
sql/sql_yacc.yy:
  Make sure that lex->option_type always gets set in 'SET TRANSACTION ...'

2 files changed, 39 insertions, 0 deletions

diff --git a/mysql-test/r/bdb.result b/mysql-test/r/bdb.result
index 2bba44d36e9..41f7369c686 100644
--- a/mysql-test/r/bdb.result
+++ b/mysql-test/r/bdb.result
@@ -1895,3 +1895,21 @@ t1	CREATE TABLE `t1` (
 ) ENGINE=BerkeleyDB DEFAULT CHARSET=latin1
 drop table t1;
 set storage_engine=MyISAM;
+create table t1 (a int) engine=bdb;
+set session transaction isolation level repeatable read;
+set transaction isolation level serializable;
+begin;
+select @@tx_isolation;
+@@tx_isolation
+SERIALIZABLE
+insert into t1 values (1);
+set transaction isolation level read committed;
+ERROR 25001: Transaction isolation level can't be changed while a transaction is in progress
+rollback;
+begin;
+select @@tx_isolation;
+@@tx_isolation
+REPEATABLE-READ
+insert into t1 values (1);
+rollback;
+drop table t1;
diff --git a/mysql-test/t/bdb.test b/mysql-test/t/bdb.test
index 3167682f816..2a987e8e7a6 100644
--- a/mysql-test/t/bdb.test
+++ b/mysql-test/t/bdb.test
@@ -973,3 +973,24 @@ drop table t1;
 
 # End varchar test
 eval set storage_engine=$default;
+
+#
+# Bug #7955: SET TRANSACTION ISIOLATION LEVEL lives longer than next
+# transaciton
+#
+create table t1 (a int) engine=bdb;
+set session transaction isolation level repeatable read;
+set transaction isolation level serializable;
+begin;
+select @@tx_isolation;
+insert into t1 values (1);
+--error ER_CANT_CHANGE_TX_ISOLATION
+set transaction isolation level read committed;
+rollback;
+begin;
+select @@tx_isolation;
+insert into t1 values (1);
+rollback;
+drop table t1;
+
+# End of 5.0 tests