[GRASS-user] the performance of displaying vector attributes - with MySQL no difference!!

[Zbigniew Perski]

On Tue, 2006-11-14 at 10:57 +0100, Zbigniew Perski wrote:
> On Mon, 2006-11-13 at 19:52 +0100, Jarek Jasiewicz wrote:
> > > Hi again,
> > > the problem of my database is that I don't see any way to optimize it.
> > > Imagine if you have 20 thousands of xyz points and want just to
> > > visualize them in different colors (dem-like color scale). Each point
> > > has its unique x,y,z values...
> > > I tried to assign indexes for my "z" column using:
> > >  
> > > 	ALTER TABLE my_points ADD INDEX(z_ccordinate);
> > >
> > > And I don't see any difference in performance with e.g. v.univar.sh 
> > > So maybe I am doing something wrong?
> > >   
> > If I understood well from the previous post threre is a RGB column it is 
> > indexed? how much categories of rgb colors you have. If you have as many 
> > categories as values this is the problem. In grass, graphical engine 
> > must assing color and render every pixel individualy
> > 
> Right I have tried both: to index my "z" column and then grassrgb as
> well. There are 30 categories and I guess it would speed up things.
> Maybe I was wrong with indexing?
> 

most probably I am doing somethig wrong with indexing:

mysql> ALTER TABLE PS_points ADD INDEX(grassrgb);
Query OK, 161884 rows affected (7.96 sec)
Records: 161884  Duplicates: 0  Warnings: 0

zero duplicates: it is strange because I have 30 categories!

Thanks

Z.


> Thanks
> 
> Zbigniew
> 
> 
>