这与另一个超过3年的问题非常相似：What's a good general way to look SQLAlchemy transactions, complete with authenticated user, etc?
我正在开发一个应用程序，我想将所有更改记录到特定的表中。目前有一个really good "recipe" that does versioning，但我需要修改它，而不是记录更改发生时的日期时间以及进行更改的用户ID。我使用了SQLAlchemy打包的history_meta.py示例，并将其记录为时间而不是版本号，但我无法确定如何传入用户ID。
我上面提到的问题建议在会话对象中包含用户ID。这很有意义，但我不知道该怎么做。我尝试过像session.userid = authenticated_userid(request)之类的简单内容，但在history_meta.py中，该属性似乎不再出现在会话对象上。
我正在Pyramid框架中完成所有这些工作，而我正在使用的会话对象被定义为DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))。在视图中，我执行session = DBSession()，然后继续使用session。 （我不确定这是否必要，但这是正在发生的事情）
以下是我修改过的history_meta.py，以防有人发现它有用：
from sqlalchemy.ext.declarative import declared_attr
from sqlalchemy.orm import mapper, class_mapper, attributes, object_mapper
from sqlalchemy.orm.exc import UnmappedClassError, UnmappedColumnError
from sqlalchemy import Table, Column, ForeignKeyConstraint, DateTime
from sqlalchemy import event
from sqlalchemy.orm.properties import RelationshipProperty
from datetime import datetime
def col_references_table(col, table):
for fk in col.foreign_keys:
if fk.references(table):
return True
return False
def _history_mapper(local_mapper):
cls = local_mapper.class_
# set the "active_history" flag
# on on column-mapped attributes so that the old version
# of the info is always loaded (currently sets it on all attributes)
for prop in local_mapper.iterate_properties:
getattr(local_mapper.class_, prop.key).impl.active_history = True
super_mapper = local_mapper.inherits
super_history_mapper = getattr(cls, '__history_mapper__', None)
polymorphic_on = None
super_fks = []
if not super_mapper or local_mapper.local_table is not super_mapper.local_table:
cols = []
for column in local_mapper.local_table.c:
if column.name == 'version_datetime':
continue
col = column.copy()
col.unique = False
if super_mapper and col_references_table(column, super_mapper.local_table):
super_fks.append((col.key, list(super_history_mapper.local_table.primary_key)[0]))
cols.append(col)
if column is local_mapper.polymorphic_on:
polymorphic_on = col
if super_mapper:
super_fks.append(('version_datetime', super_history_mapper.base_mapper.local_table.c.version_datetime))
cols.append(Column('version_datetime', DateTime, default=datetime.now, nullable=False, primary_key=True))
else:
cols.append(Column('version_datetime', DateTime, default=datetime.now, nullable=False, primary_key=True))
if super_fks:
cols.append(ForeignKeyConstraint(*zip(*super_fks)))
table = Table(local_mapper.local_table.name + '_history', local_mapper.local_table.metadata,
*cols
)
else:
# single table inheritance. take any additional columns that may have
# been added and add them to the history table.
for column in local_mapper.local_table.c:
if column.key not in super_history_mapper.local_table.c:
col = column.copy()
col.unique = False
super_history_mapper.local_table.append_column(col)
table = None
if super_history_mapper:
bases = (super_history_mapper.class_,)
else:
bases = local_mapper.base_mapper.class_.__bases__
versioned_cls = type.__new__(type, "%sHistory" % cls.__name__, bases, {})
m = mapper(
versioned_cls,
table,
inherits=super_history_mapper,
polymorphic_on=polymorphic_on,
polymorphic_identity=local_mapper.polymorphic_identity
)
cls.__history_mapper__ = m
if not super_history_mapper:
local_mapper.local_table.append_column(
Column('version_datetime', DateTime, default=datetime.now, nullable=False, primary_key=False)
)
local_mapper.add_property("version_datetime", local_mapper.local_table.c.version_datetime)
class Versioned(object):
@declared_attr
def __mapper_cls__(cls):
def map(cls, *arg, **kw):
mp = mapper(cls, *arg, **kw)
_history_mapper(mp)
return mp
return map
def versioned_objects(iter):
for obj in iter:
if hasattr(obj, '__history_mapper__'):
yield obj
def create_version(obj, session, deleted = False):
obj_mapper = object_mapper(obj)
history_mapper = obj.__history_mapper__
history_cls = history_mapper.class_
obj_state = attributes.instance_state(obj)
attr = {}
obj_changed = False
for om, hm in zip(obj_mapper.iterate_to_root(), history_mapper.iterate_to_root()):
if hm.single:
continue
for hist_col in hm.local_table.c:
if hist_col.key == 'version_datetime':
continue
obj_col = om.local_table.c[hist_col.key]
# get the value of the
# attribute based on the MapperProperty related to the
# mapped column. this will allow usage of MapperProperties
# that have a different keyname than that of the mapped column.
try:
prop = obj_mapper.get_property_by_column(obj_col)
except UnmappedColumnError:
# in the case of single table inheritance, there may be
# columns on the mapped table intended for the subclass only.
# the "unmapped" status of the subclass column on the
# base class is a feature of the declarative module as of sqla 0.5.2.
continue
# expired object attributes and also deferred cols might not be in the
# dict. force it to load no matter what by using getattr().
if prop.key not in obj_state.dict:
getattr(obj, prop.key)
a, u, d = attributes.get_history(obj, prop.key)
if d:
attr[hist_col.key] = d[0]
obj_changed = True
elif u:
attr[hist_col.key] = u[0]
else:
# if the attribute had no value.
attr[hist_col.key] = a[0]
obj_changed = True
if not obj_changed:
# not changed, but we have relationships. OK
# check those too
for prop in obj_mapper.iterate_properties:
if isinstance(prop, RelationshipProperty) and \
attributes.get_history(obj, prop.key).has_changes():
obj_changed = True
break
if not obj_changed and not deleted:
return
attr['version_datetime'] = obj.version_datetime
hist = history_cls()
for key, value in attr.items():
setattr(hist, key, value)
session.add(hist)
print(dir(session))
obj.version_datetime = datetime.now()
def versioned_session(session):
@event.listens_for(session, 'before_flush')
def before_flush(session, flush_context, instances):
for obj in versioned_objects(session.dirty):
create_version(obj, session)
for obj in versioned_objects(session.deleted):
create_version(obj, session, deleted = True)
更新
好的，似乎在before_flush（）方法中，我得到的会话类型为sqlalchemy.orm.session.Session，其中user_id附加的会话为sqlalchemy.orm.scoping.scoped_session。因此，在某些时候剥离了一个对象层。在scoped_session中将user_id分配给Session是否安全？我可以确定它不会用于其他请求吗？
答案 0 :(得分：0)
经过一系列的摆弄后，我似乎能够通过执行以下操作在scoped_session中的会话对象上设置值：
DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
session = DBSession()
inner_session = session.registry()
inner_session.user_id = "test"
versioned_session(session)
现在，在history_meta.py中传递的session对象在其上设置了user_id属性。我有点担心这是否是正确的方法，因为注册表中的对象是线程本地的，并且线程被重用于不同的http请求。
答案 1 :(得分：0)
古老的问题，但仍然很相关。
您应避免尝试将Web会话信息放置在数据库会话上。它结合了无关的关注点，每个关注点都有自己的生命周期（不匹配）。这是我在带有SQLAlchemy的Flask中使用的方法（不是Flask-SQLAlchemy，但这也应该起作用）。我试图评论金字塔在哪些方面会有所不同。
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