That's what I ended up doing. Just sending stuff a little at a time with the limit clause, but this is not ideal. Hopefully, under normal circumstances, my script would not handle tens of thousands of rows at once. For important testing purposes, we decided to send over all the rows (and that's when we see the huge slowdown). So far, the bottleneck appears to be what thor suggested: mysql fetches all of the data before returning the first row. The more I increase the limit, the longer it takes to process the first row. ...