Dynamic Metadata connected in one thread isn't in another.

[Former user]

I'm not sure this is a bug, or a wrong usage. I couldn't find any documentation/wiki entry on this.

Unhandled exception in thread started by <function do_something at 0xb7964f7c>
Traceback (most recent call last):
  File "test.py", line 16, in do_something
    print cover.select().execute()
  File "build/bdist.linux-i686/egg/sqlalchemy/sql.py", line 1175, in execute
  File "build/bdist.linux-i686/egg/sqlalchemy/sql.py", line 1063, in execute
sqlalchemy.exceptions.InvalidRequestError: This Compiled object is not bound to any engine.



#!python
import thread, time
from sqlalchemy import create_engine, BoundMetaData, DynamicMetaData, Sequence, Integer, String, Table, Column

engine = create_engine('mysql://mysql:mysql@copperhead/web_shop_development')

meta = DynamicMetaData()
meta.connect(engine)
# meta = BoundMetaData(engine) #this succeeds, is it thread-safe?

cover               = Table('cover', meta,
    Column('cover_id', Integer, Sequence('cover_seq'), primary_key=True),
    Column('name', String(128), nullable=False),
    )

def do_something():
    print cover.select().execute()

thread.start_new_thread(do_something, ())
time.sleep(3)

[Mike Bayer]

from the docs:

Another form of MetaData exits which can connect to an engine within the current thread (or "on a per-thread basis"), allowing other threads to be connected to different engines simultaneously: (example) DynamicMetaData is intended for applications that need to use the same set of Tables for many different database connections in the same process, such as a CherryPy web application which handles multiple application instances in one process.

use MetaData if you dont want thread-local.