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Re: [xsl] Using 'collection'

2015-08-29 11:49:37
Never mind, saw the error -- my dyslexia cut in.
Mark

On 8/29/2015 8:59 AM, Michael Kay mike(_at_)saxonica(_dot_)com wrote:
It’s worth putting the data in an XML database such as BaseX if you’re going to 
use it often enough to justify the cost of database loading. If you just want to use it once, 
e.g. to extract a subset of the data, then collection() should do the job - either in XQuery 
or XSLT.

To keep memory usage down, assuming you’re implementing with Saxon, the 
simplest way is to ensure that each document is unloaded from memory as soon as it has 
been processed, which you can do with saxon:discard-document:

<xsl:for-each select=“collection(‘docs?select=*.xml’)”>
   <xsl:apply-templates select=“saxon:discard-document(.)”>
</xsl:for-each>

discard-document() is a pseudo-function that returns a document unchanged, but 
with the side effect that it is marked as available for garbage collection.

Streamed processing is an alternative - but unfortunately in Saxon (until the next 
release) streaming can’t be used together with collection().

Michael Kay
Saxonica


On 29 Aug 2015, at 15:25, Mark Wilson pubs(_at_)knihtisk(_dot_)org 
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:

Hi Elliot,
I have never used XQuery or BaseX and will look into that, but what you have 
said about the XSLT looks good. I will try to sort this out and see where it 
goes. Thanks for taking the time.
Regards,
Mark

On 8/29/2015 7:13 AM, Eliot Kimber ekimber(_at_)contrext(_dot_)com wrote:
This sounds like a job better done using XQuery. A quick solution would be
to install BaseX and use its GUI to load your XML files and then apply the
query you need to the loaded docs. If you have to do complex
transformations on the things you find you can have the XQuery emit an XML
file that you can then apply an XSLT to, rather than trying to implement
the transform entirely in XQuery.

With XSLT and Saxon you could do something like:

<xsl:stylesheet ...>

<xsl:template name="run">
   <xsl:apply-templates select="collection('docs?select=*.xml')"/>
</xsl:template>

<xsl:template match="/">
   <!-- do stuff to find what you want in each doc -->
</xsl:template>
</xsl:stylesheet>

Then use the -i flag for Saxon to specify the initial template to run
("run").

The size of the documents shouldn't be a big issue, especially if you can
allocate sufficient memory to the processor. You could probably take
advantage of new streaming features in XSLT 3 and implemented in the
latest Saxon versions.

For something like this you might have to see how much virtual memory the
process requires by running it and if it fails with an out-of-memory
error, give it more until it either runs or you've run out of available
real memory.

Cheers,

Eliot

----
Eliot Kimber, Owner
Contrext, LLC
http://contrext.com




On 8/29/15, 8:36 AM, "Mark Wilson pubs(_at_)knihtisk(_dot_)org"
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:

I have been asked to isolate two elements each from a set of individual
xml files containing hundreds of elements. I thought collect() would
work, but each individual file is very large (36,000 + lines) and there
are 8000 of them. I have no idea as how to begin. I would include a
sample file, but as I said, they are very large. Where might I look to
get ideas?
Thanks,
Mark




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