ZODB 无法提交
我是第一次使用 ZODB。只是尝试使用 FileStorage 提交数据。但是当我第二次执行相同的脚本时，我无法提交新对象。这是我的脚本
from ZODB import FileStorage,DB
import transaction
storage = FileStorage.FileStorage('/tmp/test.fs')
db = DB(storage)
conn = db.open()
root = conn.root()
#root['layer']={}
root['layer']['2b']={"id":'2b','name':'some name'}
transaction.commit()
conn.close()
db.close()
storage.close()
，当我再次重复代码时，只需更改 id root['layer']['2c'] 并从 python 中出来，第二次对象不会被提交。我只有第一个对象。可能是什么原因。
I am using ZODB first time. Just trying to commit the data with FileStorage. But when I do the same script second time I am not able to commit the new object. Here is my script
from ZODB import FileStorage,DB
import transaction
storage = FileStorage.FileStorage('/tmp/test.fs')
db = DB(storage)
conn = db.open()
root = conn.root()
#root['layer']={}
root['layer']['2b']={"id":'2b','name':'some name'}
transaction.commit()
conn.close()
db.close()
storage.close()
when I repeat the code once again, with just changing the id root['layer']['2c'] and come out of the python, the second time object is not getting committed. I only have first object only. What could be the reason.
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ZODB 持久层通过挂钩到 python
__setattr__挂钩来检测更改，并在每次设置属性时将持久对象标记为已更改。但是，如果您使用像Python字典这样的原始可变对象，那么持久性机制就无法检测到更改，因为没有写入任何属性。您可以通过三个选项来解决此问题：
使用持久性映射
持久性包包含一个持久性映射类，它基本上是一个持久性的 Python 字典实现，并通过挂接到 __setitem__ 和其他映射来直接检测更改钩子。您示例中的
root对象基本上是一个持久映射。使用时，只需用持久映射替换所有字典：
通过触发挂钩强制进行更改检测
您可以再次设置密钥，或者在持久对象上再次设置属性以强制更改对象：
将持久对象标记为已更改
您可以在最近的持久对象上设置
_p_changed标志。你的根对象是你拥有的唯一持久对象，其他一切都是Python字典，所以你需要将其标记为已更改：The ZODB persistence layer detects changes by hooking into the python
__setattr__hook, marking the persistent object as changed every time you set an attribute.But if you use a primitive mutable object like a python dictionary, then there is no way for the persistence machinery to detect the changes, as there is no attribute being written. You have three options to work around this:
Use a persistent mapping
The persistent package includes a persistent mapping class, which is basically a python dictionary implementation that is persistent and detects changes directly by hooking into
__setitem__and other mapping hooks. Therootobject in your example is basically a persistent mapping.To use, just replace all dictionaries with persistent mappings:
Force a change detection by triggering the hook
You could just set the key again, or on a persistent object, set the attribute again to force the object to be changed:
Flag the persistent object as changed
You can set the
_p_changedflag on the nearest persistent object. Your root object is the only persistent object you have, everything else is python dictionaries, so you need to flag that as changed:您可能错过了
修改字典后的内容。
http://zodb.org/documentation/guide /prog-zodb.html?highlight=_p_changed#modifying-mutable-objects
You are likely missing an
after modifiying the dict.
http://zodb.org/documentation/guide/prog-zodb.html?highlight=_p_changed#modifying-mutable-objects