[sqlalchemy] isolation level not supported on MySQL 3.23

[Ids]

We were using SQLAlchemy 0.5.1 and wanted to upgrade to 0.7.8 but ran into 
the following problem.
When trying to create an engine, the mysql dialect tries to determine the 
current isolation level by issuing the SELECT @@tx_isolation; SQL statement 
(from dialects/mysql/base.py get_isolation_level()). However, this 
statement is not supported on MySQL 3.23 and therefore SQLAlchemy 0.7.8 
doesn't seem to work anymore.

We worked around this by not using SQLAlchemy anymore for our antique MySQL 
3.23 db, but this means you could also delete 3.23 from the supported 
database list. As a solution you could maybe add a try/except clause around 
it with a version check just like you do in do_commit() in 
dialects/mysql/base.py

Best regards,
Ids

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Re: [sqlalchemy] isolation level not supported on MySQL 3.23

[Michael Bayer]

On Sep 17, 2012, at 7:21 AM, Ids wrote:

 We were using SQLAlchemy 0.5.1 and wanted to upgrade to 0.7.8 but ran into 
 the following problem.
 When trying to create an engine, the mysql dialect tries to determine the 
 current isolation level by issuing the SELECT @@tx_isolation; SQL statement 
 (from dialects/mysql/base.py get_isolation_level()). However, this statement 
 is not supported on MySQL 3.23 and therefore SQLAlchemy 0.7.8 doesn't seem to 
 work anymore.
 
 We worked around this by not using SQLAlchemy anymore for our antique MySQL 
 3.23 db, but this means you could also delete 3.23 from the supported 
 database list. As a solution you could maybe add a try/except clause around 
 it with a version check just like you do in do_commit() in 
 dialects/mysql/base.py

can you let me know the specific point version of MySQL, I notice we have 
several transaction-related directives that are disabled for versions  
3.23.15..15 seems to be the first version that supports COMMIT and 
ROLLBACK.

Here's a simple patch you can try:

diff -r c72dc70dba37 lib/sqlalchemy/dialects/mysql/base.py
--- a/lib/sqlalchemy/dialects/mysql/base.py Sun Sep 16 21:15:55 2012 -0400
+++ b/lib/sqlalchemy/dialects/mysql/base.py Mon Sep 17 08:57:51 2012 -0400
@@ -1872,6 +1872,8 @@
 cursor.close()
 
 def get_isolation_level(self, connection):
+if self.server_version_info  (3, 23, 15):
+raise NotImplementedError()
 cursor = connection.cursor()
 cursor.execute('SELECT @@tx_isolation')
 val = cursor.fetchone()[0]



 
 Best regards,
 Ids
 
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