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Michael and Michael:
Thanks. I've been wondering about overall performance
of XML-enabled systems using non-traditional document
types, eg, spatial data, and I had an XML expert with
MS MVP status sleeping on my couch this weekend.
1) The effect of the binary is to increase the parser space.
The relational system doesn't care because it uses an internal
representation.
However, the binary is reputed to create a faster parse. So
while there is no query performance effect, isn't the shredder faster,
that is, assuming XML on input? Wouldn't speeding up the
pipeline be useful given 2)?
2) The effect of a document type varies by document type
and the operation. Intuitively true for any XML document type.
Since value handling depends on the value shape (the difference
in working with unstructured text vs delimited text (the case
for say long strings of vector values)), the relational model
isn't the issue: microparsing is, and again, it might be better
to be getting a binary back for some document types. The
increase in parser space could be worth it if one handles a
lot of documents of that type.
It seems that if one were to enable SQL Server spatially,
one would look for means to speed up that pipeline if the
spatial data is coming in and out as XML. I have my doubts
about articles that claim XML datatypes herald the end of
middleware and about experts that tell me Microsoft
is dumping XQuery for anything except SQL Server. Those
seem to be opinions based on business document types, and
not very large real-time maps or dynamic concept
sets.
len
From: Michael Rys [mailto:mrys@microsoft.com]
See below.
Best regards
Michael
> From: Bullard, Claude L (Len) [mailto:len.bullard@intergraph.com]
> What would be the consequences to XML datatypes in relational
> databases should an XML binary standard be created?
[Michael Rys] See my other response.
> What is the efficiency or effectiveness of the indices and
> queries given radically different kinds of XML document types
> (eg, querying over a business document in XML vs a vector
> graphic in XML)? Or put another way, how does the document
> type as instanced in the XML datatype affect querying performance?
[Michael Rys] Well, that depends heavily on the type of queries that you
plan on running. The answer is about the same as if you would ask me
about how efficient or effective the indices and the query optimizer is
for different kinds of relational schemata (OLTP, OLAP, lots of tables
with lots of columns etc.).
It certainly does affect it, but the question at the moment should be
more along the lines of: If your data fits the relational model and all
you need is a relational processor, should you store the data as XML or
should you shred it. And my answer today is: Just shred it.
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