[Sho]

No, not significantly. We have about 120.000 posts in our database, and for a user with 2500 posts it slows down the generation of the profile page by circa 0.2 seconds (according to vBMicrostats in our footer). On a not particularly powerful, shared server.

The MySQL function LENGTH() returns the length of the specified fields contents for all records in the table, SUM() adds those values together and returns the result. So it's a SUM(LENGTH(pagetext)) for the table "post" WHERE userid=X. That's a pretty fast way to do it - and it doesn't require multiple changes to newthread/editpost/newreply and new table fields to do it statically.

I'd advice against using the same technique for the postbit, but for the profile pages its good enough.

(Yes, that means spaces between words get counted as well. Well, the user had to push the space button, after all. Fair enough, eh? )