One of the disadvantages of creating a web application that's meant to run on commodity hosting is that some of your choices are severely limited. Case in point: I found out today that I can't get my web host to incrementally deliver a page when using FastCGI -- it's cached completely until it's ready for output. The options I found in Apache HTTPD to control this don't seem to be enabled for people on my tier of hosting.
This is really bad news if you want to stream a report that takes a long time to generate -- like, say, the report from the export/dump-database process.
I concocted what I think is a partial workaround, but I'm still not thrilled with it:
Range:header in the HTTP RFC to continue reading from the last point where it left off, so it doesn't have to reload the whole file.
This is as horrible a kludge as I've ever come across, but it's about the only answer I can come up with that has at least some guarantee of portability.