[Zope-dev] Catalog performance

[John Barratt]

zhimin at iss.nus.edu.sg wrote:
> Just my 2 cents observation...
> I ran this code and monitored the page "Cache extreme detail" in ZMI >
> ControlPanel > DebugInfo.
> With this method, the object was not loaded. However the intermediate
> objects that the unrestrictedTraverse() passed by were loaded into memory.
> e.g. If doc.getPath() is '/x/y/z/myobject', myobject was not loaded but x,
> y, and z were loaded into memory.
This is a good point, and for catalog based retrievals of objects may be 
difficult (but not impossible) to avoid excess objects remaining in the 
cache.  If however you are doing a walk of part of your ZODB tree 
(unlike 'randomly' accessing objects from the ZODB like this) you could 
ensure that you do a depth first traversal, then as you come back up the 
tree, traversed nodes that weren't active before the walk would be 
deactivated.

eg something like this external method :

def traverseTree(self):
     ''' Traverse the tree and do something. '''

     was_ghost = self._p_changed is None

     for ob in self.objectValues():
         traverseTree(ob)

     # XXX Do something with self here :
     self.doSomething()

     if was_ghost:self._p_deactivate()

This should ensure that any 'traversed over' nodes that were previously 
not active are de-activated.

JB.