Re[2]: [bdbxml] Indexing suggestion

Hello John,

Tuesday, April 18, 2006, 8:43:30 AM, you wrote:

> DB XML, more than any other XML database I know of, assumes it's users 
> are smart. Other XML databases I have seen only allow their users to 
> turn on value indexes, or turn them off. DB XML has chosen a more 
> flexible approach, which is to specify the name of the element or 
> attribute to index and to choose from a large number of potential 
> indexes for it.

> This flexibility does not come without penalty. Choosing the wrong 
> indexes will mean that your query will not benefit from them (or worse, 
> could be slower). Also the query optimiser in DB XML must be very smart 
> to identify which indexes it can use at a specific place in the query, 
> and then to choose the best index from amongst the available ones.

> The more specific the definition of an index, the smarter the query 
> optimiser will have to get in order to apply the index to a query. 
> Similarly, the more complex and flexible the definition of the index, 
> the harder it is to be clever about performing updates efficiently.
I understand, but is there any other way to index nodes on specific
paths such as:

/user/birth/2006/10/10

... or index functions ? Or nodes that appear with the same name on two or
more paths ? I'm afraid no, and even worst, we would indexing nodes we
don't want too. What would be the solution on these cases ?

I understand this could be hard to implement, but I really need more
flexible indexing, and I believe everybody would appreciate that, too. I
would think that the same query planner that does searches without
any indexing could be used to index those nodes and then find those
nodes when the same XPath expression is passed to it...

> A container is the unit of granularity for an index specification. If
> you have two type of documents with such different indexing needs, I 
> would suggest that you should put them in two different containers.
Currently there is no other way, but in the future I would love to have
a single container for all documents. It would greatly simplify
administration and development, give us real speed improvements...

> We always consider our user's suggestions seriously. I don't think this
> indexing scheme is appropriate for DB XML right now, however the ideas 
> behind it certainly contain some challenges and food for thought in the 
> future.
I'm sure you do consider them and I really appreciate both the product
and the support you guys offer; its just too tempting, and a must, to me
having XPath indexes :)

Thanks, John.

-- 
Best regards,
 Steve                            mailto:[email protected]


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