the isolation level is set on a cursor that's not within the usual "logged"
stream in this case. But you can see what it's set to by selecting these
variables:
from sqlalchemy import create_engine
e = create_engine("mysql://scott:tiger@localhost/test", echo=True,
isolation_level="READ UNCOMMITTED")
c = e.connect()
print c.execute("SELECT @@GLOBAL.tx_isolation, @@tx_isolation;").fetchall()
for me that returns:
[('REPEATABLE-READ', 'READ-UNCOMMITTED')]
as far as the rows being readable, I've never been one to try to anticipate the
exact effects of isolation levels like that, usually I need to open up two
consoles and do the equivalent operation manually to see which transaction sees
what.
On Sep 21, 2012, at 6:25 AM, charlax wrote:
> Hi,
>
> I'm using sqlalchemy version 0.7.8 and MySQL Ver 14.14 Distrib 5.5.25, for
> osx10.6 (i386) using readline 5.1. All my tables are using InnoDB.
>
> I'm trying to change the isolation_level, following
> http://docs.sqlalchemy.org/en/rel_0_7/dialects/mysql.html
>
> engine = create_engine(
> '[redacted]',
> echo=True,
> isolation_level="READ UNCOMMITTED"
> )
>
> connection = engine.connect()
> # Twice to make sure ...
> connection.execution_options(isolation_level="READ UNCOMMITTED")
>
> # Begin a non-ORM transaction
> trans = connection.begin()
>
> # Bind the session to the connection
> Session.configure(bind=connection)
>
> from model.toaster import Toaster
> t = Toaster()
> Session.add(t)
> Session.commit()
>
> It does not seem to be working, I can't query object created in this
> transaction from another transaction. I put "READ UNCOMMITTED" twice for
> testing.
>
> Here is the echo output:
>
> SELECT DATABASE()
> ()
> SHOW VARIABLES LIKE 'character_set%%'
> ()
> SHOW VARIABLES LIKE 'lower_case_table_names'
> ()
> SHOW COLLATION
> ()
> SHOW VARIABLES LIKE 'sql_mode'
> ()
> BEGIN (implicit)
> INSERT INTO toaster (created_at) VALUES (UTC_TIMESTAMP)
> (...)
>
> I guess I should see "SET SESSION TRANSACTION ISOLATION LEVEL <level>" but it
> does not appear.
>
> Thanks for your help!
>
> Chx
>
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