I'm using an XML pull parser which should avoid the need to slurp the whole XML file into memory, but it's not working - the script still uses over 1GB of RAM when it runs according to Activity Monitor.

I think this is because I'm still causing the full root element to be incrementally loaded into memory just in case I try and access it later.

https://effbot.org/elementtree/iterparse.htm says I should use elem.clear() as I go. It also says:

The above pattern has one drawback; it does not clear the root element, so you will end up with a single element with lots of empty child elements. If your files are huge, rather than just large, this might be a problem. To work around this, you need to get your hands on the root element.

So I will try that recipe and see if it helps.