[postgis-users] Greetings, and road data questions

[Andy Turk]

On Fri, 2002-10-18 at 12:58, Paul Ramsey wrote:

> Andy, could you re-elabourate on your multi-key experiment? In summary, 
> to do multi-key indexes with PostGIS, you need for all your indexes to 
> be GiST-based. The pgsql native btree cannot be multi-key'ed with a GiST 
> index. So you have to use the contrib/btree_index package and then build 
> a multi-key GiST-only index. At the end of the day, did this work?

Correct. GiST will do multi key indexes, but I don't think there's a set
of character operators for GiST yet. So you have to "coerce" character
data into numerical form. I believe I used the operators that come with
btree_gist in the contrib directory.

I just went back and re-read my original posting on the subject from
June:

http://postgis.refractions.net/pipermail/postgis-users/2002-June/001154.html

I misremembered things a little. The multikey index was indeed faster
than a geometry index and a sequential scan. However, the "faster"
version was still taking 10 seconds or so for a single query and I
needed nearly instantaneous responses for an interactive application.