As I mentioned in another message, undo is staying, but, as many also
mentioned in that thread, undo often doesn't work due to conflicts. I
thought I'd mention some alternatives:
- Time travel
ZODB has a number of facilities for time travel:
- Object history
There's an API for looking at changes over time. For simple
objects, recovering from a misshap can often be as simple as
copying state from an old revision. Zope 2 has (or had) a built
in view for this.
- Time traveling database connections
In ZODB 3.9, the database open method grew a optional 'at' and
'before' keyword arguments to open a connection with a view of the
database as of a particular point in time.
- zc.beforestorage
This is a storage wrapper that provides a read-only unchanging
view of a database as of a particular time. (We use it with
DemoStorage for staging new releases with customer data without
having to copy customer databases.)
- Truncation
Although there isn't an API, truncating a file-storage database as
of a particular time is pretty easy:
import ZODB.FileStorage, ZODB.TimeStamp
tid = repr(ZODB.TimeStamp.TimeStamp(y, m, d, h, min, s))
it = ZODB.FileStorage.FileIterator(path, tid)
f = open(path, 'r+b')
f.seek(it._pos)
f.truncate()
This is certainly easier and more precise than restoring from a
backup.
Maybe FileStorage should get an API for this. I'm working on a
storage implementation based on Berkeley DB and it has a truncate
function, mainly because truncation isn't so easy for this
implementation and I need it for some benchmarking I'm doing.
Jim
--
Jim Fulton
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