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> I'm neutral here, but for an opposing view see "XML Parsing:
> A Threat to
> Database Performance" [1] by Matthias Nicola of IBM. From the
> abstract:
>
> "XML parsing is generally known to have poor performance
> characteristics
> relative to transactional database processing. Yet, its potentially
> fatal impact on overall database performance is being
> underestimated. We
> report real-word database applications where XML parsing
> performance is
> a key obstacle to a successful XML deployment..."
>
> -- Ron
Thanks for the reference. The paper puzzles me, though. In section 4.1 they
say that:
* parsing a 100K document typically takes 175K instructions
* inserting a row into a relational table requires 30K to 200K instructions.
I would have expected that in a system using shredding, a 100K XML document
would result in say 200 rows being added to the database, giving an insert
cost of 6M to 40M instructions compared with a parsing cost of 175K
instructions, broadly in line with the "two orders of magnitude" that I
guessed in my original post. Clearly I'm thinking of a different kind of
application from the one that they studied.
Michael Kay
http://www.saxonica.com/
>
> [1]
> http://lists.w3.org/Archives/Public/www-ws/2004Oct/att-0032/MN
> icola_CIKM_2003_1_.pdf
>
> Michael Kay wrote:
> > I would be very surprised if XML parsing contributes
> anything noticeable to
> > the cost of a database load (in shredding mode). Except
> possibly for a
> > pathological XML document containing 3 nodes and 3 billion bytes.
> >
> > I haven't looked at the latest products from MS or Oracle,
> but my experience
> > of database loading with complex data and a realistic level
> of indexing is
> > that it's a couple of orders of magnitude slower than XML
> parsing. You can
> > improve that with a custom loader that bypasses SQL and
> does a lot of
> > heavy-duty sorting and merging to minimize head movement on
> the disk (does
> > anyone still do that?), but I think it's still true that
> the parsing cost is
> > immaterial.
>
>
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