[Sqlalchemy-tickets] Issue #3866: session.refresh(obj) spawns new connection that are held until session is closed (zzzeek/sqlalchemy)

[literg <iss...@bi...>]

New issue 3866: session.refresh(obj) spawns new connection that are held until session is closed
https://bitbucket.org/zzzeek/sqlalchemy/issues/3866/sessionrefresh-obj-spawns-new-connection

literg:

Environment: MySQL 14.14, SQLAlchemy 1.0.11, 1.0.16, 1.1.4

When using session.refresh(obj) inside session, new connection is spawned and are held until the end of session.

Code that i used:

```
#!python
session = session_maker()
try:
    yield session
    session.commit()
    for obj in session:
        session.refresh(obj)
except Exception as e:
    session.rollback()
    raise e
finally:
    session.close()

```


```
#!python

with make_session(...) as session:
        for mapped in [self._mapper.map(obj) for obj in objects]:
            saved_entities.append(mapped)
            session.add(mapped)
        session.flush()
```

Hint: The curious thing is that when i use session.commit() after session.refresh(obj) the connection is reused by next session.refresh(obj) invocation.