Martijn Faassen wrote:
Jim Fulton wrote:

Martijn Faassen wrote:

In general, I'd like the catalog to remain fairly small and free of logic.
I wanted to say this in the other thread you started on cataloging, but
didn't get to it.  Ideally, a catalog wouldn't have any query logic
at all.  People should be able to invovate on query algorithms without
affecting catalogs.

This is already clear;

Cool. Just making sure. :)

> I've been trying to do so in the project I'm
working on, though I'm more focusing on a sensible query language (well, of Python objects) than performance algorithms.

Cool.  I really wish someone would pick up on Aaron Waters Gadfly 2 work.
I strongly suspect that there are some interesting bits to mine there.

At the same time I believe Zope 3 *does* need query systems built in eventually. While it's fine to allow people to design their own query languages and algorithms, not everybody is able to do this, and those who are able to don't always want to.


> Even if they did, I don't want us
to end up with 5 different query systems either.

Hm. I wouldn't mind a bit of they addressed different needs.

So, while I agree that a query language in the core should not exclude someone from building something better, I do believe a catalog query language package is needed in the core.

I agree that a good query mechanism should be in the core, but it should be
a separate component. It should not be in the catalog.

(To be absolutely clear: I also think the RDF avenues being explored are very interesting, and I don't want to imply that this is not an interesting direction, but I do think we need something for the plain catalog too)


Hm, perhaps this isn't ideal either, as this would get hairy in case of a query that spans multiple catalogs -- which catalog will be asked in that case for a list of all documents?

I think in the particular case of "not", you have to have an implicit or
explicit set that you are subtracting something from.  The "right" set is
application specific.  In any case, I think the query logic should be
in separate query components.

I agree that the catalog should remain nice and simple.

That said, catalogs right now already have an implicit concept of 'everything indexed', which for instance is already used for re-indexing, it's just not made available to someone who wants to build something on it.

Welllll, it has a concept of of everything that could be indexed.
It generally won't index everything in the intids.

The extent catalog makes this more explicit by defining an extent, so perhaps this is the way to go.

I suspect so.

> The extent could be a query parameter to
help the query engine figure out what to do in case of 'not'. For simple use cases, the extent can be constructed from the intid utility, perhaps.

It would be helpful if someone could explain the motivations behind the extent catalog, by the way -- this information seems to be missing in zc.catalog. Am I at all on the right track with my thinking on it?

What information?


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