On Mon, Aug 9, 2010 at 11:27 PM, Michael Bayer <[email protected]> wrote:
>
> On Aug 10, 2010, at 12:03 AM, Jon Nelson wrote:
>
>> I tried setting isolation_level to SERIALIZABLE in my create_engine
>> options, while using psycopg2.
>> However, an strace clearly shows that it is using READ COMMITTED.
>> Is setting the isolation_level not supported with psycopg2?
>
>
> Here's a test:
>
> eng = create_engine('postgresql://....', isolation_level='SERIALIZABLE',
> echo=True)
> print eng.execute('show transaction isolation level').scalar()
>
> for me it returns 'serializable'.
Aha, but in psycopg2, transactions ALWAYS get a new transaction level
(set on the psycopg2 connection object with set_isolation_level). Add
to the above:
conn = eng.connect()
t = conn.begin()
print conn.execute('show transaction isolation level').scalar()
...
Mine shows:
read committed
And, of course, strace doesn't lie (much).
I have a patch! It's probably wrong, but it works (there should
probably be more checking on the actual *value* before we go about
using getattr, but here it is):
diff -r 753e46f6868c lib/sqlalchemy/dialects/postgresql/psycopg2.py
--- a/lib/sqlalchemy/dialects/postgresql/psycopg2.py Mon Aug 09
20:32:37 2010 -0400
+++ b/lib/sqlalchemy/dialects/postgresql/psycopg2.py Mon Aug 09
23:37:10 2010 -0500
@@ -207,6 +207,12 @@
psycopg = __import__('psycopg2')
return psycopg
+ def do_begin(self, conn):
+ if self.isolation_level:
+ extensions = __import__('psycopg2.extensions').extensions
+ level = getattr(extensions, 'ISOLATION_LEVEL_' +
self.isolation_level.upper())
+ conn.set_isolation_level(level)
+
def on_connect(self):
base_on_connect = super(PGDialect_psycopg2, self).on_connect()
if self.dbapi and self.use_native_unicode:
--
Jon
--
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sqlalchemy?hl=en.
