On Mon, May 10, 2010 at 4:58 PM, Jim Fulton <j...@zope.com> wrote: ... > The first thing to understand is that options like cache-size and > cache-size bytes are suggestions, not limits. :) In particular, they > are only enforced: > > - at transaction boundaries, > > - when an application creates a savepoint, > > - or when an application invokes garbage collection explicitly via the > cacheGC or cacheMinimize methods. > > Note that objects that have been monified but not committed won't be > freed even if the suggestions are exceeded. > > The reason that ZODB never frees objects on it's own is that doing so > could lead to surprising changes to object state and subtle > bugs. Consider: > > def append(self, item): > self._data.append(item) # self._data is just a Python dict > # At this point, ZODB doesn't know that self has changed. > # If ZODB was willing to free an object whenever it wanted to, > # self could be freed here, losing the change to self._data. > self._length += 1 > # Now self is marked as changed, but too late if self was > # freed above.
I meant to add that it might be interesting to error or warn when a cache gets much larger than a suggestion. Jim -- Jim Fulton _______________________________________________ For more information about ZODB, see the ZODB Wiki: http://www.zope.org/Wikis/ZODB/ ZODB-Dev mailing list - ZODB-Dev@zope.org https://mail.zope.org/mailman/listinfo/zodb-dev
