ExtractValue Runs Significantly Slower via JDBC than via C API

Hi,

I've been experimenting with the new XML features of MySQL and I've
noticed that queries using ExtractValue take noticeably longer when
querying the database through JDBC than when querying via the C API.

Does anyone know why this might be the case? Does the Connector/J
driver do any query parsing before sending the query to the server?

Here are the queries I'm testing with:

-- Retrieve XML by filtering on data in the XML itself
select xml from apnews
where ExtractValue(xml, '//entry/updated') >= curdate()
order by ExtractValue(xml, '//entry/updated') desc;

-- Retrivieve XML by filtering on indexed cols
select xml from apNewsWithIndexes
where updated >= curdate() order by updated desc;

And here are the tables I'm working with:

CREATE TABLE IF NOT EXISTS apNews (
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
xml MEDIUMTEXT NOT NULL
);

CREATE TABLE IF NOT EXISTS apNewsWithIndexes (
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
newsgroup VARCHAR(255) NOT NULL,
updated DATETIME NOT NULL,
xml MEDIUMTEXT NOT NULL,
INDEX(newsgroup), INDEX(updated)
);

Basically, I just want to see if it's feasible performance-wise to
execute queries by filtering on text data contained within XML
columns, instead of having separate indexed columns for filtering
results.

I have test code and data available if anyone is sufficiently interested.

Thanks,
Ben S.

PS. This is a dup of a post I recently added over at
http://forums.mysql.com/list.php?44.  I figured that this would
probably be a good place for it also.

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