Re: [bdbxml] xmldb like collections?

> George Feinberg wrote:
>
>>> The challenge I see in equating containers to collections is  
>>> that  in xmldb an index spans all collections in a db. In bdbxml,  
>>> it  doesn't seem you could have an index that spans containers.
>>>
>> It does not.  If you so choose, you could implement an XML:DB  
>> index  by adding
>> the same index to all known containers.
>> George
>>
>
> Thanks, this is very usefull to understand. So one last question,  
> is there any loss of performance if I search an index which spans  
> multiple containers as opposed to all my XML residing in one  
> container?

It'd be N index lookups vs 1, where N is the number of containers.
However, index lookups are quite fast.
The trickier part is rewriting a query to reference the containers  
themselves.
There is no "query all known/open containers" concept.  That would have
to be built into the implementation of the XML:DB API.
You could either rewrite the query to include hard-coded paths, or
write it to use a variable for the collection/container name, and
put a loop into the query.

You mentioned in an earlier message this:

> This is much different than in xmldb, the concept of collection is  
> within the database instance itself, there is 1 to many  
> relationship between the db instance and its collections in xmldb.
>
> The challenge I see in equating containers to collections is that  
> in xmldb an index spans all collections in a db. In bdbxml, it  
> doesn't seem you could have an index that spans containers.

Can you please provide an API reference for Indexes and their scope,  
as well as query scope in the
XML:DB interface?

George



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