>>>>> "CM" == Chris McDonough <[EMAIL PROTECTED]> writes:
>> Completely agreed. My disagreement is portraying the counter
>> problem as impossible with the zodb. I think some people, as
>> evidenced by some of the responses, are willing to live with the
>> tradeoffs. Other people will find managing a log file on disk to
>> be a more manageable solution.
CM> It would be best to make make a dual-mode undoing and nonundoing
CM> storage on a per-object basis.
I'd really like to do this for ZODB4, but it seems hard to get it into
FileStorage, without adding automatic incremental packing to
FileStorage.
Example: Object A is marked as save enough revisions to do a single
undo. When a transaction updates A and makes older revisions
unnecessary, there's no obvious way to remove them without doing a
pack. We could write a garbage collector that removed unneeded things
(as opposed to packing everything to a particular date), but it
doesn't seem very useful if it needs to be run manually.
Also, how would you specifiy the object's packing policy? I'm
thinking an _p_revision_control attribute or something like that. If
the attribute exists on an object, it sets a particular policy for
that object.
Do individual transactions need to play in this game, too? I'm
imagining a use case where an object is marked as "no revisions" but
you want to be able to undo a particular transaction. I'm not sure if
that means :
- you can undo the transaction, but the "no revisions" object
keeps its current state.
- you can undo the transaction, and because the transaction is
specially marked as undoable, there actually is a revision
- you can't undo the transaction
The first choice seems appropriate for a counter (I think), but I'm
not sure if it makes sense for all possible revision-less objects.
Jeremy
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