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

[Harri Kiiskinen]

su, 2006-11-12 kello 20:12 +0100, perski at uranos.cto.us.edu.pl kirjoitti:
> Jarek Jasiewicz <jarekj at amu.edu.pl> wrote :
> 
> > Zbigniew Perski napisa³(a):
> > > Hi,
> > >
> > > I am facing now with following problem:
> > >
> > > I have a large databases of points (more 30 000). I would like to
> > > visualize them in colors according to different attributes using
> > > d.vect.thematc and also store rgb information in the GRASSRGB column. I
> > > noticed that both methods are incredibly slow. It is very frustrating
> > > since you have to zoom and wait ages for refreshing the monitor. My
> > > database is stored using db engine. I would like to ask you if storing
> > > the point database using different engine like postgresql or mysql will
> > > have any impact on the performance in displaying the GRASSRGB column?
> > >
> > > I did not tested it yet but I am would like to know if it have any sense
> > > to spent some time on such try?
> > >
> > > Is there any other methods to speed-up the display performance in my
> > > case? I would like to add that I checked point displaying on various
> > > hardware combinations and I did not noticed any significant difference.
> > > It is always very slow.
> > >
> > >
> > > Thanks a lot
> > >
> > >
> > > Zbigniew

> 
> Hi, I spent some time on it during last days and I sucesfully
>  introduced MySQL database to grass. Unfortunately during displaying
>  poits with colors from rgb columns THERE IS NO DIFFERENCE in
>  performance comparing to dbf engine. After adding indexes to grassrgb
>  column is still the same.
> 
> Any other ideas hoe to speed up this task?

If I understood correctly, you are linking a table with the column
GRASSRGB to your data; in that case, it is the column that is used for
the link ("cat"?) that needs the index, not the one containing the data
to be used. Or you could instead try to set it as a PRIMARY KEY for the
table, as it'll speed up the data access a lot; at least on some
previous occasions GRASS did not do this by itself, but I don't know
about the current situation with MySQL.

Harri K.