[nycphp-talk] MySQL doubt
smanes at magpie.com
Sat Jan 15 22:59:41 EST 2005
Ophir Prusak wrote:
> thanx for the explanations everyone!
> fyi, i did the following two queries which use the same columns but
> return a different number of results. Indeed the %30 rule seems to be
> the case.
If you recall, we had the same situation on Postgresql at Trafficmac
with some of those mondo adserver queries which had gobs of duped
indices. That's why I built those summary tables. I believe that most
SQL engines are smart enough to see that a flat table scan may be faster
than diving through an overpopulated index tree.
More information about the talk