[Sqlalchemy-tickets] Issue #3534: Set transaction isolation level for MSSQL? (zzzeek/sqlalchemy)

[Denis S. <iss...@bi...>]

New issue 3534: Set transaction isolation level for MSSQL?
https://bitbucket.org/zzzeek/sqlalchemy/issues/3534/set-transaction-isolation-level-for-mssql

Denis Stebunov:

I'm trying to set transaction isolation level to READ UNCOMMITTED for connection to MSSQL 2012. If I specify it as a parameter to create_engine(), I get 


```
...
File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/strategies.py", line 144, in create
    engineclass.__name__))
TypeError: Invalid argument(s) 'isolation_level' sent to create_engine(), using configuration MSDialect_pymssql/QueuePool/Engine.  Please check that the keyword arguments are appropriate for this combination of components.
```

If I specify it as a parameter to sessionmaker(), I get


```
...
  File "/usr/local/lib/python2.7/site-packages/sqlalchemy/engine/interfaces.py", line 716, in set_isolation_level
    raise NotImplementedError()
NotImplementedError
```

I tried it both with pyodbc and pymssql, and none of them worked.

As a last resort I'm using `.with_hint(myTable, 'WITH (nolock)')` for my queries (this is equivalent to READ UNCOMMITTED at query level), but unfortunately it doesn't work with relationships loaded with joinedload - hint is ignored for relationships (but successfully applied to main table in the query).

Any ideas?