I'm going to agree. I've passed DBI things such as

$yesterday = $ebh->prepare("select d1.nas_ip as d1ip, d1.date as d1dat
+e, d2.nas_ip d2ip, d2.date as d2date from scratch as d1  left join sc
+ratch1 as d2 on d1.nas_ip=d2.nas_ip");
[download]

On tables over 1 gig and never had a problem with it. I'd look into the time
it takes to execute, just like VSarkiss suggested