Dmitry Vasiliev wrote:
Jim Fulton wrote:
I've created a proposal:
http://www.zope.org/Wikis/ZODB/DecouplePersistenceDatabaseAndCache
for simplifying and decoupling the persistence and cache architectures.
I've been thinking about this for quite some time. In fact, the
ability to subclass
weakref.ref objects that appeared in Python 2.4 anticipates this. :)
I like the proposal but I don't understand some details:
- Why do you want to use '__setitem__' method instead of for example
'notify'? Is it only for "make this go fast"?
Yes, as I mentioned in the proposal.
__setitem__ is an example of a "slot". A special kind of method
that doesn't require method lookup. This means that getting hold of
the method in C is very fast. Like most slots, __setitem__ can be called
without constructing an an argument tuple, assuming that the implementation
in in C. Finally, __setitem__ doesn't return an object, thus avoiding
even the need to INCREF and DECREF the return value.
- Why are such values selected for the state constants
For backward compatibility.
(persistent.GhostState = None, persistent.ChangedState = True,
persistent.SavedState = False, persistent.ReadState = False)?
These aren't the values given in the proposal. The proposal
doesn't refer to the special values True and False, but to values with
true or false (small t and f) boolian values. For example, ChangedState
could be 1 (or 42) and SavedState could be 0, 0.0, '', () or any
other value with a boolean false value.
Thanks for the questions. This is very much a rough draft proposal.
I'm aware of one problem. I'm not going to say what it is in hopes
that, in looking for it, others will find problems I haven't spotted
yet.
Jim
--
Jim Fulton mailto:[EMAIL PROTECTED] Python Powered!
CTO (540) 361-1714 http://www.python.org
Zope Corporation http://www.zope.com http://www.zope.org
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