Re: More efficient XPATH

[Marcel Ruff <ruff at swand.lake.de>]

Peter Antman wrote:
> Hi again, long time no see,
> I am woring with XmlBlaster again (this time I might even have success
> in placing at the core of a new cool project ;-).
>
> I have been experimentling with sort of using XmlBlaster as an in memory
> XML store, and querying it with XPATH and get(). The data in the key is
> fairly big, and the queries big too.
>
> First I was a little dissapointed, having 4000 document loaded, it
> actually took between 3.5 to 4 sec. per query. Far to slow to be able to
> use against an interactive gui.
>
> Then I read some of the performance tips (linked from the site) and
> redid my queries to start with /xmlBlaster/key/. And guess what: WOAW. 
> am now down to 250-300 ms per query (There is still some overhead,
> making it take a second once in a while when I document is retrieved).
>
> But basically I wanted to say this: For those who like me naively use
> //your-element to place XPATH queries against XmlBlaster will have a 10
> fold performance hit compared to use the undocumented xmlBlaster root
> element.

This is a real difference!


In the beginning of xmlBlaster we planned to normalize the xml tree,
merging same parent nodes, and having the key-oid as lowest node.

But we never implemented it.


Example:

Two messages with following meta informations:

  <key oid="Number1">
      <Airport icao="EDDI">
        <Runway id="1">
           <WindVeloc w_id="2">
           </WindVeloc>
        </Runway>
      </Airport>
   </key>

   <key oid="Number2">
      <Airport icao="EDDI">
         <Runway id="1">
           <WindVeloc w_id="1">
           </WindVeloc>
         </Runway>
      </Airport>
   </key>

XmlBlaster could than reorganize the hierarchy for performant lookup:

      <Airport icao="EDDI">
        <Runway id="1">
           <WindVeloc w_id="2" oid_reference="Number1">
           </WindVeloc>
           <WindVeloc w_id="1" oid_reference="Number2">
           </WindVeloc>
        </Runway>
      </Airport>

We assume that in most projects most messages in xmlBlaster are
of the same problem domain.



</Marcel>

> //Peter



--
Marcel Ruff
mailto:ruff at swand.lake.de
http://www.lake.de/home/lake/swand/
http://www.xmlBlaster.org