Query in a large xml file

Question

Hello,
I'm trying to work with very large xml files which are created from csv files. These files may be very large - up to 1 GB ! Untill now I have managed to do several validations on these big xml files, and the only thing that works for me is SAX parser, DOM is out of the question because it fills up memory.
My next task is to do queries on these files, smth like:
select field1,field2 from file.xml
where field3 = 'A'
and (fileld4>'B' or field1='C')
order by field2.
I searched the net about finding out how to make queries on xml files (since I have never done queries on xml before), but I couldn't find which "query language" is best for large files. If I use XPath (XSLT) will that not cause me memory problems because XSLT represents the file as a memory object?
My idea is to parse the file with SAX and check every row if it fits the where condition and then write it immediately to a result xml file. But validating the where statement can be very complicated without using some tool. Also the order by statement is another problematic issue.
Does anyone have some more intelegent ideas about how I can do this? Please help! :(
The xml file looks like this:
<doc>
<row id ="1">
<column id="1" name="column1">value</column>
<column id="N" name="columnN">value</column>
</row>
<row id ="M">
<column id="1" name="column1">value</column>
<column id="N" name="columnN">value</column>
</row>
</doc>

Answer 1

Hi all,
Thank you very much for your replies.
First, saxon didn't work because it uses an in-memory parser, and that is what I was trying to avoid.
Different database is also out of the question, because the customer insist on XML, and also there are some files that can never be converted to a database table, because eventually with some transformations thay are changed and are not completely like the standard csv format.
I think that maybe http://exist.sourceforge.net is the rigth solution for me, but I will probably try it in the next version of my project.
For now I have managed to make the project with only SAXParser and a lot of back - end programming and it works ok, althoug it was very hard to make it, and will be harded to maintain, so I will try to look at the eXist project.
Thanks everyone for the help.