[Zope3-dev] Zope's PathIndex 'level' argument

[seb bacon]

Tres Seaver wrote:
> On Mon, 2002-11-25 at 14:27, Steve Alexander wrote:
>=20
>>I'm implementing the functionality of a PathIndex for Zope 3.
>>
>>In Zope 2, when querying a PathIndex, you can give it an optional=20
>>'level' argument in addition to the base-path that you're interested in=
=2E
>>
>>Does anyone use this 'level' argument? What are its use-cases?

> That's good, because it doesn't do anything I can describe, much less
> find a good use for.  What would be much more useful is a 'depth'
> argument (or perhaps 'maxdepth' and 'mindepth', =E0 la the Unix 'find'
> command).  ('level' is something like 'mindepth', I think).


A use case for maxdepth:

If you have a hierarchical keyword taxonomy which you are using for a=20
metadata attribute on objects, you could use it to do a 'related items'=20
query.

The following example is not particularly correct, but should give you=20
the idea:


Root
  |
  + Animal
  |  |
  |  +- Canine
  |  |    +- Dog
  |  |    +- Wolf
  |  +- Feline
  |
  + Vegetable


   query({'classification':{'query':'/Animal'}

=2E..might get all animals, including dogs and wolves

   query({'classification':{'query':'/Animal', 'maxdepth':1}}

=2E..might get all canines and felines but not specifically dogs or wolve=
s

   query({'classification':{'query':'/Animal/Canine/Dog', 'maxdepth':-1}}=


=2E..might get all dogs and wolves


Of course, this may be a candidate for a different type of index - I've=20
been having a stab at a FuzzyPathIndex (Z2) along these lines.  BTW,=20
it's surprisingly difficult to optimise.

seb