On Jun 8, 2005, at 4:36 PM, Michael Kay wrote:
For example, first I have this variable to suck in outside data:
<xsl:variable name="raw-biblist">
<modsCollection xmlns="http://www.loc.gov/mods/v3";
xmlns:bib="http://purl.org/NET/xbiblio/citeproc";>
<xsl:copy-of select="$bibrecord/*/mods:mods"/>
</modsCollection>
</xsl:variable>
It's certainly not obvious that copying the source data in this way is
achieving anything useful.
The bibrecord variable that's getting copied there typically draws in
documents via document() over http (with a flatfile option as well)
with stuff like:
<xsl:copy-of
select="doc(concat("http://localhost:8080/exist/servlet/db/mods?
",
"_query=declare%20namespace%20mods=%22http://www.loc.gov/mods/
v3%22;",
"%20for%20$citekey%20in%20", $citekeys,
"%20return%20//mods:mods[(_at_)ID=$citekey]&_howmany=-1"))"/>
So in this case I'm pulling in the data from using XQuery to the eXist
REST interface.
I didn't know about sequences when I wrote it originally, and am not
sure even now if I can do this:
<xsl:variable name="bibrecord" as="element()+">
<xsl:sequence
select="doc(concat("http://localhost:8080/exist/servlet/db/mods?
",
"_query=declare%20namespace%20mods=%22http://www.loc.gov/mods/
v3%22;",
"%20for%20$citekey%20in%20", $citekeys,
"%20return%20//mods:mods[(_at_)ID=$citekey]&_howmany=-1"))"/>
</xsl:variable>
Possibly: I can't see what the apply-templates calls are doing, so
it's hard
to tell. If the apply-templates calls are creating new elements, then
there's probably no extra cost (in fact it may be cheaper) to wrap
these
elements in a document node (a temporary tree). If there's a saving to
be
made, then it will be made by avoiding creating new nodes (or copying
existing nodes).
OK. Those templates are grouping/sorting, and in one case also adding
nodes. I reorganized a few of those templates today to just pass some
(tunnel) parameters though, in part because it simplified the code.
If I understand right, so long as the node content doesn't change and
I'm just grouping and/or sorting and passing parameters, then I don't
need to use a temporary tree. Right?
Two things are worth remembering about performance engineering:
(a) don't tune your code unless it is failing to meet its performance
requirements.
(b) the only way to know whether your tuning attempts are worthwhile
is to
make measurements before and after.
OK, thanks.
Bruce
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