Spatial indexing in mnesia

[David Gould]

On Thu, Jan 04, 2001 at 10:18:42AM +0100, Ulf Wiger wrote:
> On Wed, 3 Jan 2001, David Gould wrote:
> 
> I wrote a user contrib called gridfile-1.0 which could handle spatial
> data. I'm pretty sure that noone's been using it, because I've found
> out that it doesn't work. /-: I'm working on a new version, which
> hopefully will both be correct and have better scalability.

What doesn't work? Can it be fixed just to tide us by?
 
> The idea was taken from the article "The Grid File: An Adaptable,
> Symmetric Multikey File Structure", by L. Nievergelt, H. Hinterberger,
> published in "Readings in Database Systems", 2nd Ed, pp 108-24.

Right, is that the silver cover edition, or an earlier one? Mine is at work
and I am not. Anyway, about 20 pages + or - from there is the paper by
Antonin Guttman defining R-Trees which as far as I last knew are the prefered
spatial index type.

Funny thing:  at Illustra (and later Informix), I worked with a guy
named Tony on some memory leaks and other integration bugs (we had a
difficult runtime environment) in the spatial index code, and as sometimes
happens when one is fixing someone elses bugs, I was kinda grumpy about it.
"Who wrote all this cruft, why do we let this kinda slop get checked in" and
so forth although it wasn't really that bad. It must have been about a year
later when I tumbled to the fact that "Tony" was short for "Antonin".
Sheesh. I wish I could say I was smarter now and wouldn't do that again...

 
> The really nice property was that you could do range matching in time
> proportional to the number of objects found -- not to the size of the
> table.

I will have a look. Thanks for the pointer.
 
> If somebody else is really interested, I could finish my new version.
> I could also try to make rdbms support derived indeces (difficult, due
> to problems with atomicity in trigger actions, but I have at least an
> approach to tackle that ...
> option.)

That might be useful though, there are an awful lot of non-mnesia systems
that are holding data hostage...
 
-dg

-- 
David Gould                                                 dg@REDACTED
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