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mysql> SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT * FROM information_schema.global_variables WHERE
-> variable_name = 'tx_isolation';
+---------------+-----------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+---------------+-----------------+
| TX_ISOLATION | REPEATABLE-READ |
+---------------+-----------------+
1 row in set (0.01 sec)
mysql>
Doesn't seem to be a DBI problem.
If I remeber correctly, the SQL standard only specifies minimum isolation properties for the various isolation level; giving the user a level with more isolation than requested thus isn't a violation of the standard.