I have a not dissimilar problem starting back some years ago - 1996 to be precise. We had a series of huge tables in Access - but of course it was severely limited. So in the end we used a perl script to read all the tables and merge them. As you have found, it is vastly faster.

Every year or so the problem comes back to haunt us, and this time we tried doing the merge in MySQL, on a machine similar to yours and the job takes about 7 hours. But using the in memory HASH technique - well, about 15 minutes. My task is to take about 1 million personal records that come to us from a variety of sources within a large corporation which has no integrated client management systems. Each record from each source has different data in it! So we use the script to try and build a complete single record for each person and send it back to the individual sources.

We are using a dual-Xeon system (Intel SE7505VB2 motherboard) with 4GB of RAM. RH9.0 and MySQL 4.0.16 with Perl 5.8.1

jdtoronto