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From Martin Holz <h...@fiz-chemie.de>
Subject Re: xmldb logicsheet (XMLDBTransformer is a great start)
Date Tue, 12 Feb 2002 11:59:47 GMT
Hi,

Michael Homeijer wrote:
> Have a look at the XMLDBtransformer in scratchpad, it could be easier to
> add your functionality there.

I agree.

> Additional functionality for the XMLDBTransformer could be:
> - resolving nested xml queries and/or structures (ie. get the collection
> and then get a document)
> - adding stuff dbxml provides at the command line, ie. listing, adding,
> removing and querying collections
>
> To do this two changes have to be made to the transformer:
> 1. implementing it in a way that commands can easily be added to it. (How
> about innerclasses that handle a command?)
> 2. you should be able to use results from a query or a command in the next
> query.

The standard way in Cocoon to do this, is chaining of Transformers. This 
requires, that you know at deploy time, how deep your queries are nested. 
However you should write a purpose build generator/transformer anyway, if 
your queries are very complicated and nested .  

Martin Holz wrote:
> > I see one problem with the source concept, if you are
> > retrieveing lots of
> > resources from the same collection. There are three steps to
> > get a resource from xindice;
> >
> > 1) register database
> > 2) get collection
> > 3) get document
> >
> > Typical performance numbers are:
> > 1) Need  158.0 ms for Database.
> > 2) Need 1962.0 ms for Collection.
> > 3) Need 294.0 ms for Document.
> >
> > Time for 1) drops dramatically after the first call.
> > Time for 3) is unavoidable. Time for creating a collection
> > drops too, if you
> > call it more than once, but is still high. So you want to
> > keep the collection
> > open, if you need to get documents  from this collection  often.
> >
> > You could configure a generator  to cache a collection.
> > That does not work with current implementation,  but it would
> > be straight
> > forward to add.  I can't see, how to add this capability to
> > the source URL.



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