On Thu, Aug 6, 2009 at 9:28 AM, Gustavo Rahal <gra...@linux.vnet.ibm.com>wrote:
> Em Ter, 2009-08-04 às 06:28 -0400, Jim Fulton escreveu: > > On Mon, Aug 3, 2009 at 9:09 PM, Gary Poster<gary.pos...@gmail.com> > wrote: > > > > > > On Aug 3, 2009, at 3:00 PM, Gustavo Rahal wrote: > > ... > > > Practically, using the BTrees that the ZODB provides will typically > > > have the behavior you want for the first and third gotcha. For the > > > second gotcha, we typically give each connection to the ZODB its own > > > random starting point stored on a volatile (disposable) attribute for > > > the index, and each connection increments that point. Look at the > > > code in zope.intid, for instance: _generateId in > http://svn.zope.org/zope.intid/trunk/src/zope/intid/__init__.py?rev=100049&view=auto > > > > > > Gustavo, > > > > Note that a simpler variation on this is to assign the values > > randomly. Assigning them sequentially from a random starting point is > > an optimization to reduce the number of BTree nodes read and updated > > by a particular client. > > > > Jim > > > > Thanks for the responses. I realized that I'm mixing Zope3 with ZODB. So > I should have asked if Zope3 offers anything in the uniqueness direction > and I found out that apparently it does. Anyway, it was good to know how > to deal with uniqueness in ZODB "standalone" > > pg 61 of Zope3 Web Component Architecture > > Schema field parameters > > "unique -> Specifies whether the values in a collection must be unique > or not. Applicable to all collection fields (including sequence fields)" > > I guess that is what I wanted correct? > depends on what your looking for. if your looking for a value to be within a collection on a single persistent object, you can utilize this, but at a cost of write concurrency, as it creates a chokepoint for multiple writers. for multiple persistent objects in the object database you'll need something additional. gary's reply gives a more technical understanding of the solutions. another simple solution is to use the unique value as the object's key within its container. cheers, kapil
_______________________________________________ Zope3-users mailing list Zope3-users@zope.org https://mail.zope.org/mailman/listinfo/zope3-users
