[Zope-dev] zope.catalog in ZTK

[Chris McDonough]

We teased out all this ZMI- and event-handling related behavior in 
repoze.catalog.  r.catalog consumes no events, and disuses the IIntIds utility. 
  It's otherwise a lot like zope.catalog.  It might be a good starting point if 
you want more control.

FWIW, we use this code heavily in several production apps, it's not a "throw it 
over the wall" sort of things.  It has good test coverage.

http://pypi.python.org/pypi/repoze.catalog/0.7.1


Albertas Agejevas wrote:
> Hi all,
> 
> zope.catalog is a crucial part of ZTK, as it adds the equivalent of
> RDBMS SELECT queries to our ODB based apps.  However in my opinion its
> default setup is suboptimal as a generic library in ZTK, because it is
> hardwired up for ZMI "point and click" operation.  As soon as you
> create and register an ICatalog utility, every ObjectAddedEvent and
> ObjectModifiedEvent will trigger stuffing the object into intids, and
> each intid registration event will trigger an attempt to index an
> object.  When you add an index to the catalog, it gets reindexed
> automatically.  Because these behaviours are implemented by event
> handlers, there is no way for an app to override or disable them.
> 
> There is an "opt out" mechanism for keeping objects out of the catalog
> (INoAutoIndex, INoAutoReindex marker interfaces), but curiously the
> latter does not inherit from the former,so your object can be indexed
> on modification even if you made it provide INoAutoIndex.
> 
> Automatically stuffing all newly added objects into the int ids
> utility and then further into the catalog is bad, because, first, it
> cripples any alternative uses of the int ids utility, turns it into
> purely a catalog accessory, and second, places some restrictions on
> containers and contained objects due to the persistent oid based key
> reference implementation.
> 
> About a year ago zope.app.catalog as been moved to zope.catalog.  I
> think during this move there was a unique opportunity to leave these
> event handlers behind in zope.app.catalog, so that the "no .app"
> version is free of these forced choices.  But perhaps it's not too
> late to do in now?  After all, no stable version of Zope 3 / ZTK
> codebase has been released after this move?  People relying on
> automatic indexing would have to register a couple of event handlers
> in their configurations (or include zope.app.catalog), but the rest of
> us would be able to choose the policy of how and when the objects are
> registered with IntIds and indexed in the catalog.
> 
> Albertas