[Sqlalchemy-tickets] Issue #4073: regression in bulk update, evaluator disallows literal_column (zzzeek/sqlalchemy)

[Michael B. <iss...@bi...>]

New issue 4073: regression in bulk update, evaluator disallows literal_column
https://bitbucket.org/zzzeek/sqlalchemy/issues/4073/regression-in-bulk-update-evaluator

Michael Bayer:

```
#!python

from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


class A(Base):
    __tablename__ = 'a'
    id = Column(Integer, primary_key=True)
    x = Column(Integer)
    y = Column(Integer)

e = create_engine("sqlite://", echo=True)
Base.metadata.create_all(e)


s = Session(e)
s.add(A(x=1, y=2))
s.commit()

s.query(A).update({A.x: literal_column('y')})

```

result:


```
#!

Traceback (most recent call last):
  File "test.py", line 22, in <module>
    s.query(A).update({A.x: literal_column('y')})
  File "/home/classic/dev/sqlalchemy/lib/sqlalchemy/orm/query.py", line 3366, in update
    update_op.exec_()
  File "/home/classic/dev/sqlalchemy/lib/sqlalchemy/orm/persistence.py", line 1324, in exec_
    self._do_pre_synchronize()
  File "/home/classic/dev/sqlalchemy/lib/sqlalchemy/orm/persistence.py", line 1399, in _do_pre_synchronize
    "Could not evaluate current criteria in Python. "
sqlalchemy.exc.InvalidRequestError: Could not evaluate current criteria in Python. Specify 'fetch' or False for the synchronize_session parameter.

```

this affects openstack nova and the soft_delete() method in oslo.db which uses this.