Re: fool-toleranced optimizer

Neil Conway <neilc(at)samurai(dot)com> writes:

> In any case, when this problem does occur, it is obvious to the user that
> something is wrong, and no harm is done.

I don't see why you say that. The whole complaint here is that it's *not*
obvious something is wrong and there *is* damage until it's realized.

If I run a query like this on a busy database backing a web site it could
easily kill the web site.

Or if I start this query and expect it to take an hour then after 2-3 hours
when I finally get suspicious I've just wasted 2-3 hours...

Or if I add it to the list of nightly jobs I could lose all the other jobs
that night that are preempted by this heavy query running for too long.

> Given a complex SQL query, it might take a bit of examination to determine
> which join clause is missing -- but the proper way to fix that is better
> query visualization tools (perhaps similar RH's Visual Explain, for
> example). This would solve the general problem: "the user didn't write the
> query they intended to write", rather than a very narrow subset ("the user
> forgot a join clause and accidentally computed a cartesian product").

I'm unconvinced any tool can make humans infallible.

--
greg