Re: [boost] RTL

From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2005-10-20 17:26:44

"Calum Grant" <calum_at_[hidden]> wrote

> I frankly have no idea how I would implement that problem in SQL, but
> then this was a problem you chose to be very difficult to solve using a
> SQL notation.

I am not an SQL expert, but should be something like this (if I remember
correctly):

SELECT number, name, city, COUNT(*) AS cnt
FROM mytable a, mytable b
WHERE [the long condition based on coordinates]
GROUP BY a.number
ORDER BY cnt DESC;

Then you hope that the optimizer figures out how to not compare every
possible pair ;-)

This exact statement I modeled in RTL, but RTL also specifies HOW to do
things in addition to WHAT to do, so I was able to do a smartrer
(range-based) query.

I am thrilled with your performance results, though (although I consider
them the results of a by-hand solution).  Did you completely avoid
calculating the distance?  If so, I think any such solution would provide
only approximate result (although it might happen to be a pretty good
approximation).

Regards,
Arkadiy