[Zope-dev] ZTables and/or Catalog plugable brains?

[Jay, Dylan]

> -----Original Message-----
> From: Casey Duncan [mailto:c.duncan@nlada.org]
> Sent: Friday, 5 October 2001 10:55 PM
> To: Jay, Dylan; 'zope-dev@zope.org'
> Subject: Re: [Zope-dev] ZTables and/or Catalog plugable brains?
> 
> 
> On Thursday 04 October 2001 07:34 pm, Jay, Dylan allegedly wrote:
> >
> > I tried using ZClasses but it seems to run slow and take up 
> space. Instead
> > I'm  using Catalog (without ZCatalog) to contain the data. 
> I'm presuming
> > this will be quite efficient (comments welcome).
> 
> Yup that should be pretty efficient. Plus you can index and 
> query the thing 
> fairly easily.
> >
> > Now to my question, How do Catalog plugable brains work? 
> I've looked but
> > can't see what the brain class has to look like to work. My 
> first attempts
> > don't seem to work. The classes are created but don't 
> contain the data. Is
> > the record data passed into the constructor?
> 
> I'm not an expert on brains per se, but my understanding is 
> that they allow 
> you to wrap functionality from a particular class around data 
> stored in a 
> table (such as a Catalog or an external database) without 
> making each record 
> an instance of the class.
> 
> This is how, when the Catalog returns data, you get the 
> getURL and getObject 
> methods for each record (among others). TinyTable and Z SQL 
> Methods also 
> support this functionality, and it is exposed in the 
> management interface.
> 
> This would allow you to store the actual data as regular 
> metadata elements in 
> the Catalog, and get objects out when you query it. It would 
> avoid storing 
> the data twice, once in the objects and again in the metadata 
> and all of the 
> disadvantages this causes in terms of storage and synchronization.

But what is the API? I understand that for SQLMethods you just have a class
that assumes the existance of attributes that have the same name as you
result fields. I tried doing this with the Catalog code but it seem to
doesn't work. Am I doing it right or the the Catalog brains work
differently?