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Bug #20837 Apparent change of isolation level during transaction

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SET TRANSACTION ISOLATION LEVEL is used to temporarily set
the trans.iso.level for the next transaction.  After the
transaction, the iso.level is (re-)set to value of the 
session variable 'tx_isolation'.

The bug is caused by setting the thd->variables.tx_isolation 
field to the value of the session variable upon each
statement commit.  It should only be set at the end of the
full transaction.

The fix has been to remove the setting of the variable in
ha_autocommit_or_rollback if we're in a transaction, as it 
will be correctly set in  either ha_rollback or 
ha_commit_one_phase.  

If, on the other hand, we're in  autocommit mode, tx_isolation 
will be explicitly set here.
This commit is contained in:
Magne Mahre
2009-11-30 12:30:28 +01:00
parent 4bb0e504ae
commit 8c24f5d14a
3 changed files with 65 additions and 2 deletions
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31
mysql-test/r/innodb_mysql.result
View File

@ -2273,4 +2273,35 @@ END|
DROP PROCEDURE p1;
DROP VIEW v1;
DROP TABLE t1,t2;
#
# Bug #20837 Apparent change of isolation
# level during transaction
#
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
CREATE TABLE t1 (s1 INT) ENGINE=InnoDB;
INSERT INTO t1 VALUES (1),(2);
COMMIT;
SET @@autocommit = 0;
COMMIT;
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
START TRANSACTION;
SELECT * FROM t1;
s1
1
2
Should be READ UNCOMMITTED
SELECT @@tx_isolation;
@@tx_isolation
READ-UNCOMMITTED
INSERT INTO t1 VALUES (-1);
Should be READ UNCOMMITTED
SELECT @@tx_isolation;
@@tx_isolation
READ-UNCOMMITTED
COMMIT;
Should now be REPEATABLE READ
SELECT @@tx_isolation;
@@tx_isolation
REPEATABLE-READ
DROP TABLE t1;
End of 5.1 tests

26
mysql-test/t/innodb_mysql.test
View File

@ -536,4 +536,30 @@ DROP PROCEDURE p1;
DROP VIEW v1;
DROP TABLE t1,t2;
--echo #
--echo # Bug #20837 Apparent change of isolation
--echo # level during transaction
--echo #
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
CREATE TABLE t1 (s1 INT) ENGINE=InnoDB;
INSERT INTO t1 VALUES (1),(2);
COMMIT;
SET @@autocommit = 0;
COMMIT;
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
START TRANSACTION;
SELECT * FROM t1;
--echo Should be READ UNCOMMITTED
SELECT @@tx_isolation;
INSERT INTO t1 VALUES (-1);
--echo Should be READ UNCOMMITTED
SELECT @@tx_isolation;
COMMIT;
--echo Should now be REPEATABLE READ
SELECT @@tx_isolation;
DROP TABLE t1;
--echo End of 5.1 tests

8
sql/handler.cc
View File

@ -1369,7 +1369,13 @@ int ha_autocommit_or_rollback(THD *thd, int error)
if (thd->transaction_rollback_request && !thd->in_sub_stmt)
(void) ha_rollback(thd);
}
}
else if (!(thd->options & (OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN)))
{
/*
If we're in autocommit mode, reset tx_isolation
to the default value
*/
thd->variables.tx_isolation= thd->session_tx_isolation;
}
#endif