XML : Fast comparison xml files with ruby and saving to db

I'm looking for method for fast comparison xml files with ruby. I have 2 files (40MB), each about 100,000 rows. Each element consists of 20 attributes. Files obtained from different databases. I would like to compare them and find out what data has changed, to update them in the database.Tell me, what's going to help me?

With xml I've never worked, so in my head is an idea for comparison of each line (after the parsing and checking with the database). But I think it is very slow.