Re: sql in php with paging

["Walden H. Leverich" <WaldenL@xxxxxxxxxxxxxxx>]

25ms, ouch! but ok, you raise a valid point. However, to me the
difference is that of the disconnected HTTP world. How do you know when
you can release those connections? 20 minutes of inactivity? 120
minutes? 24 hours? What's your "session" expiration time? It's these
questions that make the web so fun. :-)

Say 10 new people show up on your site every 10 minutes. If you're
willing to set your session timeout for 10 minutes then you'll need to
handle 10 people on your site. Cool. Now, same arrival rate, but you
aren't willing to kick them off the site unless they've been inactive
for 60 minutes, now you need to handle 60 people on your site. Chances
are 50 of them aren't doing anything, and never will be, but just in
case... 

Now expand the math... 6,000 people arrive every hour. Average time on
site, 10 minutes, but you won't kick them off until they've been
inactive for 4 hours. Holding the connection open until session times
out, you'll need 24,000 connections. Now go back to your
25ms/transaction time. 6,000 people every hour spread evenly, that's 100
people per minute, or 1.66 people per second. Since, on average, a
single connection can handle 40 people per second (1000ms / 25ms per
transaction) you could actually handle all 6000 people with one
connection. Now sure, they're not perfectly spread out over the hour,
and not all transactions take exactly 25ms, and of course each person
will perform more than one transaction, but still, the open/close/open
process uses several orders of magnitude fewer connections than the
hold-per-session model.

-Walden