If you're not adverse to Java, the XOM XML library has a nice
NodeFactory class that you can override and control the processing of
the XML document.  For instance, it will let you parse a very large
XML document like

<root>
  <rec></rec>
  <rec></rec>
  ...
</root>

only keeping a <rec> at a time in memory.  You control the node
building process so can throw away the one's you're done with.  It's
friendlier than SAX and what I use for processing very large
documents.

Cf. http://www.xom.nu/apidocs/nu/xom/NodeFactory.html

Kevin



On Fri, Jun 8, 2012 at 2:36 PM, Kyle Banerjee <[log in to unmask]> wrote:
> I'm working on a script that needs to be able to crosswalk at least a
> couple hundred XML files regularly, some of which are quite large.
>
> I've thought of a number of ways to go about this, but I wanted to bounce
> this off the list since I'm sure people here deal with this problem all the
> time. My goal is to make something that's easy to read/maintain without
> pegging the CPU and consuming too much memory.
>
> The performance and load I'm seeing from running the files through LibXML
> and SimpleXML on the large files is completely unacceptable. SAX is not out
> of the question, but I'm trying to avoid it if possible to keep the code
> more compact and easier to read.
>
> I'm tempted to streamedit out all line breaks since they occur in
> unpredictable places and put new ones at the end of each record into a temp
> file. Then I can read the temp file one line at a time and process using
> SimpleXML. That way, there's no need to load giant files into memory,
> create huge arrays, etc and the code would be easy enough for a 6th grader
> to follow. My proposed method doesn't sound very efficient to me, but it
> should consume predictable resources which don't increase with file size.
>
> How do you guys deal with large XML files? Thanks,
>
> kyle
>
> <rant>Why the heck does the XML spec require a root element,
> particularly since large files usually consist of a large number of
> records/documents? This makes it absolutely impossible to process a file of
> any size without resorting to SAX or string parsing -- which takes away
> many of the advantages you'd normally have with an XML structure. </rant>
>
> --
> ----------------------------------------------------------
> Kyle Banerjee
> Digital Services Program Manager
> Orbis Cascade Alliance
> <[log in to unmask]>[log in to unmask] / 503.999.9787